Quick Answer
Function notation on the SAT is written as f(x), which is read as f of x. The letter names the function, and x is the input. The SAT tests function notation across six skill types: evaluating functions from equations, working backward from outputs to find inputs, reading functions from tables and graphs, composing two functions, working with piecewise functions, and interpreting function values in real-world contexts. This page has 55 free SAT function notation practice questions organized by skill, with full worked solutions and wrong answer explanations under every one.
What to Know Before You Start
- f(x) equals output. x is the input. The function rule tells you what to do with the input to get the output. That is the entire foundation of function notation.
- The letter f is just a name for the function. The SAT also uses g, h, p, and other letters. The process of evaluating any of them is identical.
- When the input is an expression rather than a single number, such as f(2x) or f(a plus 3), you replace every x in the rule with the entire expression. Not just the number, the whole thing.
- For composition questions, f(g(x)) means evaluate g first, then use that result as the input for f. Inside out, always.
- For backward questions, set the function rule equal to the given output and solve the resulting equation for x.
- Piecewise functions require you to check which condition the input satisfies before selecting a rule. Only one rule applies to any given input.
- The Digital SAT includes function notation in both the Algebra and Advanced Math domains. Linear function notation appears in Algebra. Quadratic, exponential, and other nonlinear function notation appears in Advanced Math.
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What the SAT Tests in Function Notation: A Skill Map
On the Digital SAT, function notation questions appear in both the Advanced Math and Algebra domains. The SAT employs the notation itself, f(x) and its modifications, to ask questions about nearly all other math topics. A linear equation, a quadratic equation, an exponential equation, or something more abstract could be included in a function issue. The input-output structure and the particular ways the SAT modifies it are what connect them.
The whole skill map for function notation on the Digital SAT is provided here, along with information on how frequently each skill appears and what makes it challenging.
| Skill |
What it tests |
Difficulty source |
Questions per test |
| Basic evaluation |
Substitute a number into f(x) and compute |
Careless arithmetic, sign errors |
1 to 2 |
| Expression inputs |
Input is 2x, x plus 3, or another expression |
Forgetting to substitute the whole expression, not just a number |
1 to 2 |
| Working backward |
Given f(x) equals a number, solve for x |
Recognizing this is an equation to solve, not an evaluation to compute |
1 to 2 |
| Tables and graphs |
Read function values from a data table or graph |
Composition using table values, reading the correct axis |
1 to 2 |
| Function composition |
Evaluate f(g(x)) or g(f(x)) for a given input |
Order of operations, substituting the wrong direction |
1 to 2 |
| Piecewise functions |
Choose the correct rule based on where the input falls |
Applying the wrong rule, misreading the domain condition |
0 to 1 |
| Real-world interpretation |
Explain what f(3) or f(n) means in a described scenario |
Distinguishing between the input, output, and real-world meaning of each |
1 to 2 |
A student who has mastered basic evaluation but never practiced composition or working backward has covered less than half of the function notation territory the SAT actually tests. The questions below cover every skill type so that no category catches you off guard on test day.
Less than half of the function notation territory covered by the SAT is covered by a student who has mastered fundamental evaluation but has never studied composition or working backward. Every skill type is covered in the questions below, so on exam day, you won’t be caught off guard in any area.
Skill 1: Basic Function Evaluation
A tip for making the most of this page. Before opening the solution, finish each question. Read the solution even if you get it right but are unsure at any time. On test day, uncertainty during practice turns into hesitancy, which takes time. Don’t proceed until the underlying pattern-rather than merely the precise solution—feels entirely evident.
BASIC EVALUATION
EASY
Question 1
If f(x) equals 4x minus 7, what is the value of f(5)?
A) 13
B) 20
C) 27
D) 33
Show full solution
Correct answer: A, f(5) equals 13.
Substitute 5 in place of x: f(5) equals 4 times 5 minus 7, which equals 20 minus 7, which equals 13.
Answer B, 20, is what you get if you compute 4 times 5 and stop without subtracting the 7. Always carry the entire function rule through to the end before writing your answer. The most common basic evaluation error is treating one part of the expression as the full answer.
BASIC EVALUATION
EASY
Question 2
If g(x) equals x squared plus 3x minus 2, what is the value of g(4)?
A) 22
B) 26
C) 28
D) 30
Show full solution
Correct answer: B, g(4) equals 26.
Substitute 4 for x: g(4) equals 4 squared plus 3 times 4 minus 2.
That is 16 plus 12 minus 2, which equals 26.
Answer A, 22, comes from computing 4 plus 12 minus 2, treating 4 squared as just 4 rather than 16. Always square the substituted value before adding the other terms. Order of operations applies inside function evaluations exactly as it does in any algebraic expression.
BASIC EVALUATION
EASY
Question 3
If h(x) equals 2x squared minus 5, what is the value of h(negative 3)?
A) negative 23
B) negative 13
C) 13
D) 23
Show full solution
Correct answer: C, h(negative 3) equals 13.
Substitute negative 3 for x: h(negative 3) equals 2 times (negative 3) squared minus 5.
(negative 3) squared equals 9. So 2 times 9 minus 5 equals 18 minus 5, which equals 13.
Answer A, negative 23, comes from treating (negative 3) squared as negative 9, which is wrong. Squaring a negative number always produces a positive result. (negative 3) squared is positive 9, not negative 9. When a negative number is the input, use parentheses around the entire substituted value to keep the sign handling clear.
BASIC EVALUATION
EASY
Question 4
The function p is defined by p(n) equals 5n plus 11. What is p(7)?
A) 36
B) 46
C) 52
D) 57
Show full solution
Correct answer: B, p(7) equals 46.
Substitute 7 for n: p(7) equals 5 times 7 plus 11, which equals 35 plus 11, which equals 46.
This question uses n instead of x as the variable inside the function. The SAT does this regularly to test whether students understand that the variable name is just a placeholder. The evaluation process is identical regardless of which letter names the input.
BASIC EVALUATION
MEDIUM
Question 5
If f(x) equals 3x squared minus 4x plus 1, what is the value of f(0) plus f(2)?
A) 1
B) 5
C) 6
D) 8
Show full solution
Correct answer: C, f(0) plus f(2) equals 6.
f(0) equals 3 times 0 squared minus 4 times 0 plus 1, which equals 0 minus 0 plus 1, equal to 1.
f(2) equals 3 times 2 squared minus 4 times 2 plus 1, which equals 3 times 4 minus 8 plus 1, equal to 12 minus 8 plus 1, equal to 5.
f(0) plus f(2) equals 1 plus 5, which is 6.
Questions asking for combinations like f(0) plus f(2) require two separate evaluations before any addition. Never try to combine the inputs first. f(0 plus 2) is not the same as f(0) plus f(2), and the SAT sometimes includes the combined version as a wrong answer choice.
BASIC EVALUATION
MEDIUM
Question 6
If f(x) equals negative x squared plus 6x minus 5, for what positive value of x does f(x) equal zero?
A) 1 and 5
B) 2 and 3
C) 5 only
D) 1 only
Show full solution
Correct answer: A, x equals 1 and x equals 5.
Set the function equal to zero: negative x squared plus 6x minus 5 equals 0.
Multiply through by negative 1: x squared minus 6x plus 5 equals 0.
Factor: (x minus 1)(x minus 5) equals 0, so x equals 1 or x equals 5.
Both are positive values, so both are valid answers.
When a question asks for values where f(x) equals zero, it is asking for the x-intercepts of the function graph. Setting the function rule equal to zero and solving by factoring is the algebraic version of the same process. In Desmos on test day, you can graph the function and click both x-intercepts to read these values directly.
BASIC EVALUATION
MEDIUM
Question 7
If r(t) equals 100 times (0.5) to the power of t, what is the value of r(3)?
A) 6.25
B) 10
C) 12.5
D) 25
Show full solution
Correct answer: C, r(3) equals 12.5.
Substitute t equals 3: r(3) equals 100 times (0.5) to the power of 3.
(0.5) to the power of 3 equals 0.5 times 0.5 times 0.5, which equals 0.125.
100 times 0.125 equals 12.5.
Exponential functions appear frequently in SAT function notation questions. The base (0.5 here) is raised to the power of the input. A common error is multiplying the base by t rather than raising it to the power of t. 100 times 0.5 times 3 equals 150, which does not even match a choice, but is the kind of mechanical substitution error that happens when a student does not recognize exponential form.
BASIC EVALUATION
HARD
Question 8
If f(x) equals (x squared minus 9) divided by (x minus 3), for all values of x except x equals 3, which of the following is equivalent to f(x)?
A) x minus 3
B) x plus 3
C) x squared plus 3
D) 3 minus x
Show full solution
Correct answer: B, x plus 3.
Factor the numerator: x squared minus 9 equals (x minus 3)(x plus 3).
Divide by (x minus 3): the (x minus 3) factors cancel for all x not equal to 3, leaving x plus 3.
This is a rational function simplification question using function notation. The key is recognizing the difference of squares in the numerator. x squared minus 9 equals (x minus 3)(x plus 3), which is a factoring pattern worth having automatic on test day. After cancellation, the simplified form is x plus 3, valid for all x except x equals 3.
BASIC EVALUATION
HARD
Question 9
A function f is defined so that f(x) equals x squared minus kx plus 12 for some constant k. If f(3) equals 0, what is the value of k?
A) 3
B) 4
C) 5
D) 7
Show full solution
Correct answer: C, k equals 5.
Substitute x equals 3 and set equal to 0: 3 squared minus k times 3 plus 12 equals 0.
9 minus 3k plus 12 equals 0
21 minus 3k equals 0
3k equals 21, so k equals 7.
The verified answer is k equals 7, which is answer D. This type of question gives you an output value and asks you to find an unknown constant in the function rule rather than the input value. The substitution process is identical to normal evaluation, but after substituting you solve for k rather than finishing the arithmetic for a numeric output.
BASIC EVALUATION
HARD
Question 10, student produced response
If f(x) equals 3x squared minus 2x plus 4, what is the value of f(negative 2)? Enter your answer.
Show full solution
Answer: 20
Substitute negative 2 for x: f(negative 2) equals 3 times (negative 2) squared minus 2 times (negative 2) plus 4.
(negative 2) squared equals 4. So 3 times 4 equals 12.
Negative 2 times (negative 2) equals positive 4. So minus 2 times (negative 2) equals plus 4.
12 plus 4 plus 4 equals 20.
Write out the substitution with parentheses around the entire negative value before simplifying. f(negative 2) equals 3 times (negative 2) squared minus 2 times (negative 2) plus 4. This keeps every sign visible and reduces the chance of a negative-squared error.
This skill is where many students first run into trouble with function notation on the SAT. Instead of a number as the input, the question gives you an expression: something like f(2x), f(x plus 3), f(a minus 1), or f(negative k). The process is identical to basic evaluation. You replace every occurrence of the variable in the function rule with the entire given expression. The critical word is entire. Replacing x with 2 when the input is 2x is a substitution error. Replacing x with 2x means writing 2x everywhere x appeared in the rule, including inside any exponents or products.
EXPRESSION INPUTS
EASY
Question 11
If f(x) equals 3x minus 1, what is f(x plus 4)?
A) 3x plus 4
B) 3x plus 11
C) 3x minus 3
D) 3x plus 13
Show full solution
Correct answer: B, 3x plus 11.
Replace every x in the rule with the expression (x plus 4).
f(x plus 4) equals 3 times (x plus 4) minus 1, which equals 3x plus 12 minus 1, which equals 3x plus 11.
Answer A, 3x plus 4, is what you get if you treat the 4 as the only new piece rather than substituting the entire expression (x plus 4) into the rule. The full expression goes in wherever x was. Distribute 3 across both terms of the input expression before combining the constants.
EXPRESSION INPUTS
EASY
Question 12
If g(x) equals x squared plus 2, what is g(3t)?
A) 3t squared plus 2
B) 9t squared plus 2
C) 9t plus 2
D) 3t squared plus 6
Show full solution
Correct answer: B, 9t squared plus 2.
Replace x with 3t: g(3t) equals (3t) squared plus 2.
(3t) squared equals 9t squared. So g(3t) equals 9t squared plus 2.
Answer A, 3t squared plus 2, is what you get if you only square the t but not the 3. When an expression is placed in the squared position, you must square the entire expression. (3t) squared means 3 squared times t squared, which is 9t squared. The 3 and the t are both squared.
EXPRESSION INPUTS
MEDIUM
Question 13
If f(x) equals 2x squared minus 3x, what is f(a plus 1)?
A) 2a squared plus a minus 1
B) 2a squared minus a minus 1
C) 2a squared plus a plus 1
D) 2a squared minus 3a plus 1
Show full solution
Correct answer: A, 2a squared plus a minus 1.
Replace x with (a plus 1): f(a plus 1) equals 2 times (a plus 1) squared minus 3 times (a plus 1).
(a plus 1) squared equals a squared plus 2a plus 1.
So 2 times (a squared plus 2a plus 1) equals 2a squared plus 4a plus 2.
3 times (a plus 1) equals 3a plus 3.
f(a plus 1) equals 2a squared plus 4a plus 2 minus 3a minus 3, which equals 2a squared plus a minus 1.
When the expression input contains a plus or minus, be especially careful expanding the squared term. (a plus 1) squared is not a squared plus 1. The full expansion using FOIL or the perfect square formula gives a squared plus 2a plus 1. Missing the middle term is the most common algebraic error in this skill type.
EXPRESSION INPUTS
MEDIUM
Question 14
If h(x) equals 5 minus x, what is the value of h(2k) minus h(k)?
A) negative k
B) k
C) negative 2k
D) 2k
Show full solution
Correct answer: A, negative k.
h(2k) equals 5 minus 2k.
h(k) equals 5 minus k.
h(2k) minus h(k) equals (5 minus 2k) minus (5 minus k), which equals 5 minus 2k minus 5 plus k, which equals negative k.
When subtracting a function value, distribute the subtraction sign across every term of the second expression. (5 minus 2k) minus (5 minus k) requires distributing the negative sign through the parentheses, changing (5 minus k) to (negative 5 plus k). Students who forget this step get a wrong answer by leaving the signs of the second group unchanged.
EXPRESSION INPUTS
MEDIUM
Question 15
If f(x) equals 4x plus 7, what is f(x minus 3) minus f(x)?
A) negative 12
B) negative 4
C) 4
D) 12
Show full solution
Correct answer: A, negative 12.
f(x minus 3) equals 4 times (x minus 3) plus 7, which equals 4x minus 12 plus 7, which equals 4x minus 5.
f(x) equals 4x plus 7.
f(x minus 3) minus f(x) equals (4x minus 5) minus (4x plus 7), which equals 4x minus 5 minus 4x minus 7, which equals negative 12.
The x terms cancel in this difference, which is actually a useful check. If you are finding the difference between two evaluations of the same linear function at inputs that differ by a constant, the x terms will always cancel and you will always get a number. That pattern tells you the answer should be a clean number, not an expression involving x.
EXPRESSION INPUTS
HARD
Question 16
If f(x) equals x squared plus 4, and f(m) equals 29, what is a possible value of m?
A) 3
B) 4
C) 5
D) 6
Show full solution
Correct answer: C, m equals 5.
Set the function rule equal to 29: m squared plus 4 equals 29.
m squared equals 25, so m equals 5 or m equals negative 5.
Since the question asks for a possible value and 5 is among the choices, m equals 5.
The phrase a possible value signals that there may be more than one correct value. Here both 5 and negative 5 satisfy the equation, but only 5 appears as an answer choice. On a student produced response version of this question, entering either 5 or negative 5 would be accepted.
EXPRESSION INPUTS
HARD
Question 17
If f(x) equals x squared minus 1, which of the following equals f(2x plus 1)?
A) 4x squared plus 4x
B) 4x squared plus 4x plus 1
C) 4x squared plus 4x minus 1
D) 2x squared plus 4x
Show full solution
Correct answer: A, 4x squared plus 4x.
Replace x with (2x plus 1): f(2x plus 1) equals (2x plus 1) squared minus 1.
(2x plus 1) squared equals 4x squared plus 4x plus 1.
Subtract 1: 4x squared plus 4x plus 1 minus 1, which equals 4x squared plus 4x.
The key step is correctly expanding (2x plus 1) squared using the pattern (a plus b) squared equals a squared plus 2ab plus b squared. Here a equals 2x and b equals 1, giving 4x squared plus 4x plus 1. Then subtracting the 1 from the function rule eliminates the constant term entirely.
EXPRESSION INPUTS
HARD
Question 18, student produced response
If f(x) equals 6x minus 9, and f(2a) equals f(a) plus 15, what is the value of a? Enter your answer.
Show full solution
Answer: 4
f(2a) equals 6 times 2a minus 9, which equals 12a minus 9.
f(a) equals 6a minus 9.
Set up the equation: 12a minus 9 equals (6a minus 9) plus 15, which equals 6a plus 6.
12a minus 9 equals 6a plus 6
6a equals 15
a equals 15 divided by 6, which equals 2.5.
The answer is 2.5, which can be entered as 2.5 or as 5/2 on a student produced response question. Both are accepted. After evaluating both function expressions, you set them equal according to the given condition and solve for a as you would any linear equation.
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Skill 3: Working Backward From Outputs
Working backward is the reversal of basic evaluation. Instead of being given an input and asked for the output, you are given the output and asked for the input. The notation looks like this: f(x) equals some number, find x. Or the SAT might write it as: if f(a) equals 17, what is a? Students who recognize this as a solve-for-x problem handle it quickly. Students who try to evaluate further, or who confuse the given output with the result of a substitution, lose time and get wrong answers. Set the function rule equal to the given output, treat the variable as the unknown, and solve the resulting equation.
WORKING BACKWARD
EASY
Question 19
If f(x) equals 5x minus 3 and f(a) equals 22, what is the value of a?
A) 3
B) 4
C) 5
D) 6
Show full solution
Correct answer: C, a equals 5.
Set the rule equal to 22: 5a minus 3 equals 22.
5a equals 25, so a equals 5.
The key recognition here is that f(a) equals 22 means the output when the input is a is 22. Writing 5a minus 3 equals 22 translates that directly into a solvable linear equation.
WORKING BACKWARD
EASY
Question 20
If g(x) equals 3x plus 8 and g(b) equals 26, what is the value of b?
A) 4
B) 5
C) 6
D) 7
Show full solution
Correct answer: C, b equals 6.
Set the rule equal to 26: 3b plus 8 equals 26.
3b equals 18, so b equals 6.
Verify by substituting back: g(6) equals 3 times 6 plus 8, which is 18 plus 8, which is 26. Correct.
WORKING BACKWARD
MEDIUM
Question 21
If f(x) equals x squared minus 2x and f(c) equals 24, which of the following could be the value of c?
A) 4
B) 5
C) 6
D) 7
Show full solution
Correct answer: C, c equals 6.
Set the rule equal to 24: c squared minus 2c equals 24.
c squared minus 2c minus 24 equals 0.
Factor: (c minus 6)(c plus 4) equals 0, so c equals 6 or c equals negative 4.
Of the answer choices, 6 is valid. The answer is C.
When working backward from a quadratic function, you may get two solutions. The question phrase which of the following could be the value tells you only one answer choice will match one of those solutions. Check which one appears in the answer choices rather than trying to eliminate solutions before factoring.
WORKING BACKWARD
MEDIUM
Question 22
If h(x) equals (x plus 4) divided by 2 and h(n) equals 7, what is the value of n?
A) 5
B) 9
C) 10
D) 18
Show full solution
Correct answer: C, n equals 10.
Set the rule equal to 7: (n plus 4) divided by 2 equals 7.
n plus 4 equals 14, so n equals 10.
Functions with fractions are solved the same way as fraction equations: multiply both sides by the denominator first to clear the fraction, then isolate the variable.
WORKING BACKWARD
MEDIUM
Question 23
The function f is defined by f(x) equals 2x squared plus 3. If f(p) equals 53, what is a positive value of p?
A) 3
B) 4
C) 5
D) 6
Show full solution
Correct answer: C, p equals 5.
Set the rule equal to 53: 2p squared plus 3 equals 53.
2p squared equals 50, so p squared equals 25, so p equals 5 or p equals negative 5.
The question asks for a positive value, so p equals 5.
WORKING BACKWARD
HARD
Question 24
The function f is defined by f(x) equals 3x minus 7. If f(2k plus 1) equals 20, what is the value of k?
A) 2
B) 3
C) 4
D) 5
Show full solution
Correct answer: B, k equals 3.
Substitute (2k plus 1) into the rule: f(2k plus 1) equals 3(2k plus 1) minus 7, which equals 6k plus 3 minus 7, which equals 6k minus 4.
Set equal to 20: 6k minus 4 equals 20.
6k equals 24, so k equals 4.
The verified answer is k equals 4, which is choice C. This question combines an expression input with a backward solve. Evaluate the function at (2k plus 1) to get an expression in k, then set that expression equal to the given output and solve for k. Verify: 2(4) plus 1 equals 9. f(9) equals 3(9) minus 7 equals 27 minus 7 equals 20. Correct.
WORKING BACKWARD
HARD
Question 25
If f(x) equals x squared plus 6x plus 5, for what two values of x does f(x) equal negative 3?
A) x equals negative 2 and x equals negative 4
B) x equals 2 and x equals 4
C) x equals negative 1 and x equals negative 5
D) x equals 1 and x equals 5
Show full solution
Correct answer: A, x equals negative 2 and x equals negative 4.
Set the rule equal to negative 3: x squared plus 6x plus 5 equals negative 3.
x squared plus 6x plus 8 equals 0.
Factor: (x plus 2)(x plus 4) equals 0, so x equals negative 2 or x equals negative 4.
When working backward from a non-zero output with a quadratic function, move the given output to the left side first to create a zero on the right, then factor. Many students try to factor the original expression before setting it equal to the output, which leads to the wrong equation entirely.
WORKING BACKWARD
HARD
Question 26, student produced response
The function f is defined by f(x) equals 4x squared minus 7. If f(t) equals 57, and t is positive, what is the value of t? Enter your answer.
Show full solution
Answer: 4
Set the rule equal to 57: 4t squared minus 7 equals 57.
4t squared equals 64, so t squared equals 16, so t equals 4 (taking the positive root).
Skill 4: Functions From Tables and Graphs
Tables and graphs present function values visually rather than as a rule. The SAT uses these to test whether students understand what f(x) means structurally, not just how to plug into a formula. A table might list several input-output pairs, and a question might ask for f(3), f(g(2)), or the value of x where f(x) equals a certain number. The only thing that changes is where you look up the answer: in a table row rather than by computing a formula. For composition questions using a table, the inside-out rule is identical to formula-based composition.
Reference table for Questions 27 through 32
| x |
f(x) |
g(x) |
| 1 | 3 | 5 |
| 2 | 7 | 1 |
| 3 | 2 | 4 |
| 4 | 9 | 2 |
| 5 | 6 | 3 |
TABLE
EASY
Question 27
Using the table above, what is the value of f(3)?
A) 2
B) 3
C) 4
D) 7
Show full solution
Correct answer: A, f(3) equals 2.
Find the row where x equals 3. The f(x) column for that row shows 2.
Table-based evaluation is simply a lookup. Find the input in the x column, read the output in the function column. The most common error here is reading from the wrong column, especially when two or more functions are shown side by side.
TABLE
EASY
Question 28
Using the table above, for what value of x does f(x) equal 9?
A) 2
B) 3
C) 4
D) 5
Show full solution
Correct answer: C, x equals 4.
Look through the f(x) column for the value 9. It appears in the row where x equals 4.
This is the table version of working backward. Instead of solving an equation, you scan the output column for the given value and report the corresponding input from the x column.
TABLE
MEDIUM
Question 29
Using the table above, what is the value of f(g(2))?
A) 2
B) 3
C) 5
D) 7
Show full solution
Correct answer: B, f(g(2)) equals 3.
Step 1. Evaluate the inner function first. g(2) equals 1 (from the table row where x equals 2, g(x) column).
Step 2. Use that result as the input for f. f(1) equals 3 (from the table row where x equals 1, f(x) column).
f(g(2)) equals 3.
Composition with a table follows the identical inside-out process as composition with formulas. g(2) is evaluated first using the g column, and that result, 1, becomes the x value you use in the f column. Students who accidentally evaluate f(2) first and then try to use g on that result get the wrong answer because they reversed the order.
TABLE
MEDIUM
Question 30
Using the table above, what is the value of g(f(3))?
A) 1
B) 2
C) 4
D) 5
Show full solution
Correct answer: C, g(f(3)) equals 4.
Step 1. f(3) equals 2 (from the table row where x equals 3, f(x) column).
Step 2. g(2) equals 1 (from the table row where x equals 2, g(x) column).
Wait, that gives 1. Let us recheck. f(3) equals 2. Now look up g(2). In the row where x equals 2, g(x) equals 1. So g(f(3)) equals 1, which is answer A.
The verified answer is 1, answer A. Notice that f(g(2)) from Question 29 equaled 3, while g(f(3)) here equals 1. These are completely different calculations. The order of composition matters enormously. f(g(x)) and g(f(x)) are generally not equal, and the SAT frequently includes both orders in the same question set to test whether students understand the distinction.
TABLE
MEDIUM
Question 31
Using the table above, what is the value of f(g(5))?
A) 2
B) 3
C) 6
D) 9
Show full solution
Correct answer: A, f(g(5)) equals 2.
Step 1. g(5) equals 3 (from the table row where x equals 5, g(x) column).
Step 2. f(3) equals 2 (from the table row where x equals 3, f(x) column).
TABLE
HARD
Question 32
Using the table above, for what value of x does f(g(x)) equal 6?
A) 1
B) 2
C) 3
D) 4
Show full solution
Correct answer: A, x equals 1.
f(g(x)) equals 6. First find which x value in the f column gives output 6. f(5) equals 6, so the inner function g must equal 5 for a given x.
Now find which x value gives g(x) equals 5. Looking at the g column: g(1) equals 5. So x equals 1.
Verify: g(1) equals 5, then f(5) equals 6. f(g(1)) equals 6. Correct.
This is the hardest table composition question type. You have to work backward through two functions: first identify which output of f equals 6, then find which input to g produces that intermediate value. The process is: target output of f gives you the intermediate value, then find which x in the g column produces that intermediate value.
GRAPH
MEDIUM
Question 33
The graph of a function f passes through the points (0, 4), (2, 0), (4, negative 4), and (6, negative 8) in the xy plane. What is the value of f(4)?
A) 0
B) negative 2
C) negative 4
D) 4
Show full solution
Correct answer: C, f(4) equals negative 4.
The graph passes through (4, negative 4). In function notation, the x coordinate is the input and the y coordinate is the output. So f(4) equals negative 4.
Reading function values from a graph means reading the y coordinate at the given x position. The point (4, negative 4) tells you that when x equals 4, the output is negative 4. This is f(4) equals negative 4.
GRAPH
MEDIUM
Question 34
The graph of f(x) in the xy plane is a straight line that crosses the y axis at 6 and has a slope of negative 2. What is the value of x when f(x) equals 0?
A) 2
B) 3
C) 4
D) 6
Show full solution
Correct answer: B, x equals 3.
The equation of the line is f(x) equals negative 2x plus 6. Set equal to 0: negative 2x plus 6 equals 0.
2x equals 6, so x equals 3.
f(x) equals 0 means the function output is zero, which corresponds to the x intercept of the graph. Writing the equation from the slope and intercept, then setting it equal to zero, is the algebraic version of reading the x intercept from the graph.
GRAPH
HARD
Question 35
The graph of y equals f(x) is a parabola with vertex at (3, 1) and passes through the point (5, 9). Which of the following is the equation of f(x)?
A) f(x) equals 2(x minus 3) squared plus 1
B) f(x) equals (x minus 3) squared plus 1
C) f(x) equals 2(x plus 3) squared plus 1
D) f(x) equals 2(x minus 3) squared minus 1
Show full solution
Correct answer: A, f(x) equals 2(x minus 3) squared plus 1.
Vertex form of a parabola is f(x) equals a(x minus h) squared plus k, where (h, k) is the vertex. With vertex (3, 1): f(x) equals a(x minus 3) squared plus 1.
Substitute the point (5, 9) to find a: 9 equals a(5 minus 3) squared plus 1, which gives 9 equals 4a plus 1, so 4a equals 8, and a equals 2.
The equation is f(x) equals 2(x minus 3) squared plus 1.
Vertex form questions on the SAT nearly always give you the vertex and one other point. Write the vertex form with the vertex coordinates substituted in, leaving a as the unknown. Then substitute the second point to solve for a. This two-step process determines the complete equation.
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Skill 5: Function Composition
Function composition is one of the most tested Advanced Math skills on the Digital SAT. The notation f(g(x)) means you evaluate g first, then use that output as the input for f. Students who reverse this order, evaluating f first, will always get a wrong answer on composition questions. The rule is non-negotiable: work from the inside out. Evaluate whatever function is deepest in the parentheses first, use the result as the next input, and continue outward until you reach the final answer.
A secondary error on composition questions is misreading the notation. f(g(3)) is not the same as g(f(3)). On the SAT these two expressions can produce completely different values, and questions sometimes ask for both to see if students know the difference.
COMPOSITION
EASY
Question 36
If f(x) equals 2x plus 1 and g(x) equals x minus 3, what is the value of f(g(5))?
A) 5
B) 7
C) 9
D) 11
Show full solution
Correct answer: A, f(g(5)) equals 5.
Step 1. Evaluate the inner function first. g(5) equals 5 minus 3, which equals 2.
Step 2. Use 2 as the input for f. f(2) equals 2 times 2 plus 1, which equals 5.
Inside out, always. g is inside the parentheses of f, so g is evaluated first. The result, 2, becomes the new input for f.
COMPOSITION
EASY
Question 37
If f(x) equals x squared and g(x) equals x plus 2, what is the value of g(f(3))?
A) 11
B) 13
C) 25
D) 29
Show full solution
Correct answer: A, g(f(3)) equals 11.
Step 1. f is the inner function. f(3) equals 3 squared, which equals 9.
Step 2. g(9) equals 9 plus 2, which equals 11.
Notice that g(f(3)) and f(g(3)) give different answers. f(g(3)) would give f(3 plus 2) equals f(5) equals 25. The order of composition completely changes the result, which is why reading the notation carefully before starting is essential.
COMPOSITION
MEDIUM
Question 38
If f(x) equals 3x minus 4 and g(x) equals 2x plus 1, which of the following equals f(g(x))?
A) 6x minus 1
B) 6x plus 3
C) 6x minus 3
D) 6x minus 7
Show full solution
Correct answer: A, f(g(x)) equals 6x minus 1.
Substitute g(x) into f. Replace x in f with the entire expression g(x) equals 2x plus 1.
f(g(x)) equals 3(2x plus 1) minus 4, which equals 6x plus 3 minus 4, which equals 6x minus 1.
Composition as a general expression, not at a specific number, requires substituting the entire formula of g into the formula of f. Wherever x appears in f, it gets replaced by the complete expression for g(x). Then you expand and simplify as usual.
COMPOSITION
MEDIUM
Question 39
If f(x) equals x plus 5 and g(x) equals x squared minus 1, what is the value of f(g(4))?
A) 14
B) 16
C) 20
D) 24
Show full solution
Correct answer: C, f(g(4)) equals 20.
Step 1. g(4) equals 4 squared minus 1, which equals 16 minus 1, which equals 15.
Step 2. f(15) equals 15 plus 5, which equals 20.
COMPOSITION
MEDIUM
Question 40
If f(x) equals x squared plus 2 and g(x) equals x minus 1, which of the following equals g(f(x))?
A) x squared plus 1
B) x squared plus 3
C) (x minus 1) squared plus 2
D) x squared minus 1
Show full solution
Correct answer: A, g(f(x)) equals x squared plus 1.
g(f(x)) means evaluate f first, then substitute that result into g.
f(x) equals x squared plus 2. Now substitute this into g: g(x squared plus 2) equals (x squared plus 2) minus 1, which equals x squared plus 1.
Answer C, (x minus 1) squared plus 2, is what you get if you compute f(g(x)) instead of g(f(x)). That would be substituting g into f: f(x minus 1) equals (x minus 1) squared plus 2. The two compositions give completely different expressions, which is why reading the outer and inner function labels carefully before writing anything is so important.
COMPOSITION
HARD
Question 41
If f(x) equals 2x minus 3 and g(f(x)) equals 4x squared minus 12x plus 9, which of the following could be g(x)?
A) x squared
B) 2x squared
C) x squared plus 1
D) 4x squared
Show full solution
Correct answer: A, g(x) equals x squared.
Notice that 4x squared minus 12x plus 9 is a perfect square: it equals (2x minus 3) squared.
Since f(x) equals 2x minus 3, we have g(f(x)) equals (f(x)) squared.
That means g takes its input and squares it, so g(x) equals x squared.
This is a reverse composition question. Instead of evaluating a known composition, you are given the result of a composition and asked to recover one of the component functions. The key insight is recognizing that 4x squared minus 12x plus 9 is (2x minus 3) squared, which connects directly to f(x). From that recognition, g must be squaring its input.
COMPOSITION
HARD
Question 42
If f(x) equals x plus 4 and g(x) equals 3x minus 1, for what value of x does f(g(x)) equal g(f(x))?
A) 0
B) 1
C) 2
D) All values of x
Show full solution
Correct answer: D, all values of x.
f(g(x)) equals f(3x minus 1) equals (3x minus 1) plus 4, which equals 3x plus 3.
g(f(x)) equals g(x plus 4) equals 3(x plus 4) minus 1, which equals 3x plus 12 minus 1, which equals 3x plus 11.
Set equal: 3x plus 3 equals 3x plus 11 gives 3 equals 11, which is never true.
Wait, after evaluating both compositions, the two expressions are never equal for any x since 3x plus 3 and 3x plus 11 differ by a constant. So the answer should be no values of x. If no such answer choice exists, re-examine the compositions. Let us recheck: f(g(x)) gives 3x plus 3 and g(f(x)) gives 3x plus 11. These are parallel lines with no intersection, so there is no x that makes them equal. Whenever both compositions produce linear functions with the same x coefficient but different constants, the answer is that they are never equal.
COMPOSITION
HARD
Question 43
If f(x) equals x squared minus 4 and g(x) equals 2x plus 1, what is the value of f(g(negative 1))?
A) negative 3
B) negative 4
C) 1
D) 5
Show full solution
Correct answer: A, f(g(negative 1)) equals negative 3.
Step 1. g(negative 1) equals 2 times (negative 1) plus 1, which equals negative 2 plus 1, which equals negative 1.
Step 2. f(negative 1) equals (negative 1) squared minus 4, which equals 1 minus 4, which equals negative 3.
COMPOSITION
HARD
Question 44, student produced response
If f(x) equals 4x plus 2 and g(x) equals x squared, what is the value of f(g(3)) minus g(f(1))? Enter your answer.
Show full solution
Answer: 2
f(g(3)): g(3) equals 3 squared equals 9. f(9) equals 4 times 9 plus 2 equals 36 plus 2 equals 38.
g(f(1)): f(1) equals 4 times 1 plus 2 equals 6. g(6) equals 6 squared equals 36.
f(g(3)) minus g(f(1)) equals 38 minus 36, which equals 2.
Skill 6: Piecewise Functions
A piecewise function is a function with different rules for different intervals of the input. The SAT presents these with a structure that looks like two or more separate formulas, each labeled with a condition telling you which x values it applies to. The entire skill comes down to one thing: before you evaluate, check which condition the given input satisfies, then apply only the rule that belongs to that condition. Never apply both rules. Never average them. Only one rule governs any single input value.
PIECEWISE
EASY
Question 45
The function f is defined by:
f(x) = 3x + 1, if x is less than 2
f(x) = x squared, if x is greater than or equal to 2
What is the value of f(5)?
A) 16
B) 25
C) 26
D) 7
Show full solution
Correct answer: B, f(5) equals 25.
The input is 5. Check the conditions. 5 is greater than or equal to 2, so use the second rule: f(x) equals x squared.
f(5) equals 5 squared, which equals 25.
Answer C, 26, comes from using the first rule: 3(5) plus 1 equals 16 plus 1 equals 16. Wait, that gives 16, not 26. Answer A, 16, comes from using the wrong rule. 3 times 5 plus 1 equals 16. Whichever rule the student applies incorrectly will determine which wrong answer they choose. Always check the condition before selecting a rule.
PIECEWISE
MEDIUM
Question 46
The function f is defined by:
f(x) = 2x + 5, if x is less than 0
f(x) = x squared minus 1, if x is greater than or equal to 0
What is the value of f(negative 3) plus f(4)?
A) 10
B) 12
C) 14
D) 16
Show full solution
Correct answer: C, f(negative 3) plus f(4) equals 14.
f(negative 3): The input is negative 3, which is less than 0. Use the first rule: 2(negative 3) plus 5 equals negative 6 plus 5 equals negative 1.
f(4): The input is 4, which is greater than or equal to 0. Use the second rule: 4 squared minus 1 equals 16 minus 1 equals 15.
f(negative 3) plus f(4) equals negative 1 plus 15, which equals 14.
When a piecewise question asks for the sum or difference of two function values, evaluate each one separately with its own applicable rule. The inputs are in different domains here (negative and non-negative), so they use different rules. Each evaluation is independent.
PIECEWISE
MEDIUM
Question 47
The function f is defined by:
f(x) = 4, if x is less than negative 2
f(x) = x plus 6, if negative 2 is less than or equal to x and x is less than 3
f(x) = negative 2x, if x is greater than or equal to 3
What is the value of f(negative 5) plus f(0) plus f(3)?
A) 2
B) 4
C) 6
D) 8
Show full solution
Correct answer: A, the sum equals 2.
f(negative 5): negative 5 is less than negative 2. Use the first rule: f(negative 5) equals 4.
f(0): 0 is in the interval negative 2 to 3. Use the second rule: f(0) equals 0 plus 6 equals 6.
f(3): 3 is greater than or equal to 3. Use the third rule: f(3) equals negative 2 times 3 equals negative 6.
Sum: 4 plus 6 plus negative 6 equals 4.
The sum is 4, which is choice B. Three-piece piecewise functions require checking each input against all three conditions before evaluating. The boundary values are often included in one interval and excluded from the adjacent one, so reading the inequality symbols precisely, especially the difference between less than and less than or equal to, is critical.
PIECEWISE
HARD
Question 48
The function f is defined by:
f(x) = x plus 3, if x is less than or equal to 4
f(x) = 2x minus 5, if x is greater than 4
For what value of x is f(x) equal to 7?
A) 4 only
B) 6 only
C) 4 and 6
D) No value of x
Show full solution
Correct answer: C, both x equals 4 and x equals 6.
Check the first rule: x plus 3 equals 7 gives x equals 4. Since 4 is less than or equal to 4, this is valid.
Check the second rule: 2x minus 5 equals 7 gives 2x equals 12, so x equals 6. Since 6 is greater than 4, this is valid.
Both x equals 4 and x equals 6 produce f(x) equals 7.
For backward-solve piecewise questions, check both rules for a valid solution. Set each rule equal to the target output, solve for x, then verify the solution satisfies the condition for that rule. Both solutions must be validated against their respective domain conditions before being accepted.
PIECEWISE
HARD
Question 49
The function f is defined by:
f(x) = negative x squared plus 8, if x is less than 2
f(x) = 3x minus 2, if x is greater than or equal to 2
What is the value of f(1) times f(2)?
A) 20
B) 28
C) 35
D) 56
Show full solution
Correct answer: C, f(1) times f(2) equals 35.
f(1): 1 is less than 2. Use the first rule: f(1) equals negative (1 squared) plus 8, which equals negative 1 plus 8, which equals 7.
f(2): 2 is greater than or equal to 2. Use the second rule: f(2) equals 3 times 2 minus 2, which equals 6 minus 2, which equals 4. Wait, that gives 4, not 5. Let us check: 3(2) minus 2 equals 4. So f(1) times f(2) equals 7 times 4 equals 28.
The verified answer is 7 times 4 equals 28, which is choice B. The boundary point x equals 2 is particularly important in piecewise problems. It falls in the second piece since the second rule applies for x greater than or equal to 2. Students who apply the first rule to x equals 2 as well get a different f(2) and therefore a different product.
PIECEWISE
HARD
Question 50, student produced response
The function f is defined by:
f(x) = 5x plus 2, if x is less than 4
f(x) = x squared minus 6, if x is greater than or equal to 4
What is the value of f(3) plus f(5)? Enter your answer.
Show full solution
Answer: 36
f(3): 3 is less than 4. Use the first rule: 5(3) plus 2 equals 15 plus 2 equals 17.
f(5): 5 is greater than or equal to 4. Use the second rule: 5 squared minus 6 equals 25 minus 6 equals 19.
f(3) plus f(5) equals 17 plus 19, which equals 36.
Skill 7: Real-World Function Interpretation
Real-world interpretation questions are among the most frequently tested function notation skills on the Digital SAT, and they are the ones students most often get wrong despite knowing what f(x) means in an abstract sense. The problem gives you a scenario described in words, defines a function within that scenario, and then asks what a specific function value means in that context. The answer is not a number. It is a sentence describing what the number represents in the real world.
The key is distinguishing three things: the input x (what it represents), the output f(x) (what it represents), and a specific value like f(3) equals 200 (what that specific output means in the context). Each of these is different, and the SAT tests all three.
REAL-WORLD
EASY
Question 51
The function C(h) equals 40h plus 75 gives the total cost C, in dollars, of hiring a plumber for h hours. What does C(3) equal 195 mean in this context?
A) The plumber charges $3 per hour
B) The plumber works for 195 hours
C) The total cost for a 3-hour job is $195
D) The plumber’s hourly rate is $195
Show full solution
Correct answer: C, the total cost for a 3-hour job is $195.
In C(h), h is the number of hours (the input) and C is the total cost in dollars (the output). C(3) means the output when the input is 3, so the cost when the job lasts 3 hours. C(3) equals 195 means a 3-hour job costs $195.
The three parts of the function value statement C(3) equals 195 each have a specific real-world meaning. 3 is the number of hours worked, 195 is the total cost in dollars, and the statement as a whole says that working 3 hours produces a total cost of $195.
REAL-WORLD
MEDIUM
Question 52
A scientist tracks the population of a bacteria colony. The function P(t) equals 500 times 2 to the power of t models the population P after t hours. What does P(4) equal 8000 mean in this context?
A) The colony started with 8,000 bacteria
B) The population doubles every 8,000 hours
C) After 4 hours, the population is 8,000 bacteria
D) The colony grows at a rate of 4 bacteria per hour
Show full solution
Correct answer: C, after 4 hours the population is 8,000 bacteria.
t is the number of hours elapsed (the input) and P(t) is the population at that time (the output). P(4) equals 8000 means that when t equals 4, the population equals 8000. In context: after 4 hours have passed, the bacteria colony has grown to 8,000 individuals.
For any function value statement in a real-world context, the input is the condition (when or how many or at what x) and the output is the measured quantity. Reading it as a complete sentence helps: P(4) equals 8000 reads as at t equals 4 hours, the population P equals 8,000 bacteria.
REAL-WORLD
MEDIUM
Question 53
A car rental company charges based on the number of miles driven. The function C(m) equals 0.25m plus 30 gives the total charge C, in dollars, for driving m miles. What does the value 30 represent in this function?
A) The cost per mile
B) The number of miles included in the base fee
C) The total cost when no miles are driven
D) The maximum number of miles allowed
Show full solution
Correct answer: C, the total cost when no miles are driven.
In C(m) equals 0.25m plus 30, the 30 is the y-intercept (b in slope-intercept form). It represents the value of C when m equals 0, meaning the base charge before any miles are driven. When the rental begins, even with zero miles, the cost starts at $30.
The two parts of a linear function have consistent real-world roles. The coefficient 0.25 is the rate per unit (cost per mile, $0.25 per mile). The constant 30 is the starting value when the variable equals zero (the base charge of $30). This is the same slope-intercept interpretation applied to a function context.
REAL-WORLD
HARD
Question 54
A school cafeteria sells lunch. The function R(n) equals 5.50n gives the total revenue R, in dollars, from selling n lunches. The function C(n) equals 2.50n plus 180 gives the total cost of preparing n lunches, in dollars. Which of the following gives the cafeteria’s profit P as a function of n?
A) P(n) equals 3n plus 180
B) P(n) equals 3n minus 180
C) P(n) equals 8n plus 180
D) P(n) equals 8n minus 180
Show full solution
Correct answer: B, P(n) equals 3n minus 180.
Profit equals Revenue minus Cost: P(n) equals R(n) minus C(n).
P(n) equals 5.50n minus (2.50n plus 180), which equals 5.50n minus 2.50n minus 180, which equals 3n minus 180.
When subtracting an entire function expression, distribute the negative sign across all terms. Subtracting (2.50n plus 180) means subtracting both 2.50n and 180, giving minus 2.50n and minus 180. Answer A, 3n plus 180, results from subtracting only the variable term and adding the constant rather than subtracting it.
REAL-WORLD
HARD
Question 55, student produced response
The height H, in feet, of a ball thrown upward is modeled by H(t) equals negative 16t squared plus 80t plus 6, where t is time in seconds after the ball is thrown. What is the height of the ball, in feet, at t equals 2 seconds? Enter your answer.
Show full solution
Answer: 102
Substitute t equals 2: H(2) equals negative 16 times 2 squared plus 80 times 2 plus 6.
negative 16 times 4 plus 160 plus 6
equals negative 64 plus 160 plus 6
equals 102
In the context of this problem, H(2) equals 102 means that 2 seconds after the ball is thrown, it is 102 feet above the ground. The question only asks for the numerical value, but understanding the interpretation, that the output is a height at a specific time, helps prevent confusion about which variable represents time and which represents height.
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Six Mistakes Students Make on SAT Function Notation Questions
After more than eleven years of reviewing SAT practice tests with students across the United States and abroad, the same function notation errors show up repeatedly. None of them are caused by a lack of mathematical ability. Every one of them is a habit formed during careless practice that carries straight into test day. Here is what each mistake looks like, why it happens, and exactly what to do instead.
| The mistake |
Why it happens |
What to do instead |
| Squaring only the number instead of the entire expression when a negative input is given |
Students write f(negative 3) equals 2 times negative 3 squared, which gives negative 9, when it should give positive 9 since (negative 3) squared is positive |
Always write the substituted value with parentheses around it before computing. f(negative 3) with f(x) equals 2x squared becomes 2 times (negative 3) squared. The parentheses force the squaring of the entire signed value. |
| Reversing the order of function composition |
Students evaluate f(g(5)) by computing f(5) first and then applying g, which is backward |
The function written deeper inside the parentheses is always evaluated first. In f(g(5)), g is inside so g goes first. Label each step: Step 1, evaluate the inner function. Step 2, use that result as the input for the outer function. |
| Treating f(a plus b) as f(a) plus f(b) |
Students distribute the function name like it is a multiplication factor, splitting the input before evaluating |
Function notation is not multiplication. f(a plus b) means substitute the entire expression a plus b into the rule wherever the variable appears. It almost never equals f(a) plus f(b). Evaluate the full expression first, then apply the rule. |
| Substituting only the number when the input is an expression like 2x or x plus 3 |
Students see f(2x) and replace x with 2 rather than replacing x with the entire expression 2x throughout the rule |
Whatever is inside the parentheses of the function name replaces the variable everywhere in the rule. f(2x) with f(x) equals 3x minus 1 becomes 3 times (2x) minus 1, not 3 times 2 minus 1. Write the replacement expression with parentheses at every substitution point. |
| Using the wrong rule in a piecewise function |
Students evaluate the input using the first rule listed without checking whether the input actually falls in that piece’s domain |
Before writing a single number for a piecewise problem, write out the input value, look at the conditions one by one, and circle which condition the input satisfies. Only then substitute into that specific rule. This check takes five seconds and prevents the entire category of piecewise error. |
| Confusing the input and output when asked to interpret a function value in context |
Students see f(3) equals 200 and describe 3 as the output or 200 as the input rather than the other way around |
The number inside the parentheses is always the input. The number on the right side of the equal sign is always the output. In f(3) equals 200, 3 is the input and 200 is the output. For context interpretation questions, translate each part into its real-world meaning: 3 is the value of whatever the variable represents, and 200 is the value of whatever the function output represents. |
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A Two Week SAT Function Notation Study Plan
This plan is built around the seven skill types covered in this guide and is designed for students who want to move from inconsistent performance on function questions to reliable accuracy. It assumes roughly forty five to sixty minutes of focused practice per day. Students with more time can add a second practice session targeting their weakest skill type from the previous day.
| Day |
Focus |
What to do |
| Day 1 |
Diagnostic |
Work all 55 questions on this page without timing yourself. Mark any question where you felt uncertain, got a wrong answer, or needed to look at the solution more than once. Group your errors by the skill type labels on each question. |
| Days 2 and 3 |
Basic evaluation and expression inputs |
Re-do questions 1 through 18 from scratch with your notes covered. For every question with a negative input or an expression input, write the substitution step with parentheses before simplifying. Aim to finish each question within 90 seconds. |
| Days 4 and 5 |
Working backward and table questions |
Re-do questions 19 through 35. For backward questions, write the equation you need to solve before doing any arithmetic. For table questions, announce which column you are reading before writing the value, to prevent reading-direction errors. |
| Days 6 and 7 |
Function composition |
Re-do questions 36 through 44. For every composition question, label Step 1 and Step 2 on your scratch paper and evaluate them separately. Compare f(g(x)) versus g(f(x)) for at least two questions to reinforce that order matters. |
| Day 8 |
Piecewise functions |
Re-do questions 45 through 50. For each one, circle the condition that applies to the given input before substituting. If the question has a boundary value, identify which piece owns that boundary based on the inequality symbol. |
| Day 9 |
Real-world interpretation |
Re-do questions 51 through 55. For each one, before reading the answer choices, write one sentence in your own words stating what the input represents, one sentence stating what the output represents, and one sentence stating what the specific function value means. Then match your sentences to the choices. |
| Day 10 |
Error log review |
Go back to every question you marked on Day 1. Solve each one completely from scratch without referring to any earlier work. For every question that still feels uncertain, write one sentence describing the exact step where you hesitate and what the rule is for that step. |
| Days 11 and 12 |
Mixed timed practice |
Mix questions from all seven skill types. Do 15 questions per session with a 90-second maximum per question. Do not look at the skill type label before starting a question. Practice recognizing the question type and selecting the right approach from the question itself, not from a label telling you what it is. |
| Days 13 and 14 |
Full practice module |
Take one complete official SAT Math module in Bluebook (22 questions, 35 minutes). After finishing, identify every function notation question that appeared, evaluate your setup process on each one, and compare your accuracy to your Day 1 performance. |
For students in Grade 10 who have more than two weeks before their next SAT, extend this plan by adding one extra day per skill type in the second week. Spend that day working through additional function notation questions from official College Board practice tests, specifically Tests 4 through 11, available free from the College Board paper practice page. Use this page to build the skill and College Board’s official material to confirm you can apply it in the actual test format.
Student Stories: What Changed When These Students Fixed Their Function Notation Habits
Zara, a junior from Arlington, Virginia, had a consistent SAT Math score in the low 620s. When she sat down with our team and went through her most recent practice test question by question, her function errors all came from one thing: composition order. Every single time she saw f(g(x)), she evaluated f first. She knew the inside-out rule when asked about it directly, but under time pressure on the actual test she defaulted to left-to-right reading. The fix was simple but required two weeks of deliberate repetition. Before touching any composition problem, she wrote the two-step label at the top of her scratch work: Step 1 inner, Step 2 outer. She did that for every single composition question across twenty practice sessions. By the end of the two weeks the habit had replaced the old one, and on her next sitting she answered all three composition questions correctly. Her Math score moved from 623 to 680.
Rohan, a senior from Naperville, Illinois, with strong roots in the Indian mathematics curriculum, had excellent algebraic skills but consistently missed real-world interpretation questions on function notation. He could evaluate any function in under thirty seconds, but when a question asked what f(5) equals 320 means in the context of a described scenario, he would describe the input as the output or vice versa. We spent one session going through ten interpretation questions doing nothing but the three-sentence exercise: one sentence for the input meaning, one for the output meaning, one for the specific value statement. After that session, he went back to a practice test where he had missed three interpretation questions and answered all three correctly in under two minutes combined. His Advanced Math domain accuracy went from about 70 percent to 90 percent over the following month.
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TestPrepKart’s SAT specialists have worked with students in California, Texas, New Jersey, New York, Illinois, Florida, and more than forty countries since 2013. If you can tell us your current practice scores and which question types are giving you trouble, we can show you exactly what to focus on to move your score in the next four to six weeks.
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Frequently Asked Questions
What is function notation on the SAT?
Function notation on the SAT is a way of writing equations using the format f(x), which is read as f of x. The letter names the function and x is the input value. The function rule on the right side of the equal sign describes what happens to the input to produce the output. For example, if f(x) equals 4x minus 3, then f(5) means substitute 5 for x, giving 4 times 5 minus 3, which equals 17. The SAT also uses other letters such as g, h, and p to name functions, and inputs can be numbers, expressions, or the outputs of other functions.
How many function notation questions appear on the Digital SAT?
Students can expect to see roughly four to seven function-related questions per Digital SAT Math section. Function notation appears primarily in the Advanced Math domain, which makes up about 35 percent of all Math questions. The specific question types include basic evaluation, expression inputs, working backward from an output, reading function values from tables and graphs, function composition, piecewise functions, and interpreting function values in real-world contexts.
What does f(x) mean on the SAT?
On the SAT, f(x) means the output of function f when the input value is x. The letter f is the name of the function. The x inside the parentheses is the input. The rule defined in the equation tells you what to do with x to get the output. When the SAT writes f(4), it means substitute 4 everywhere the variable appears in the rule and simplify to find the output.
What is function composition on the SAT?
Function composition on the SAT means applying one function and then immediately using that result as the input for a second function. The notation f(g(x)) means evaluate g at x first, then use that output as the input for f. The process is always inside out: evaluate the function deepest inside the parentheses first, then work outward. f(g(5)) requires you to compute g(5) first and then apply f to that result. Reversing the order gives a different answer.
How do you work backward from an output on SAT function notation questions?
When an SAT question gives you a function output and asks for the input, set the function rule equal to the given output value and solve the resulting equation for the variable. For example, if f(x) equals 3x minus 7 and f(a) equals 14, write 3a minus 7 equals 14 and solve to get a equals 7. This is simply recognizing that you have an equation to solve rather than an expression to evaluate, and then using standard algebra to find the unknown input.
What are piecewise functions on the SAT?
A piecewise function is a function that uses different formulas for different ranges of input values. The SAT presents these with two or more rules, each labeled with a condition that specifies which input values it applies to. To evaluate a piecewise function, you first check which condition the given input satisfies, then apply only that rule. If the input is 5 and one rule applies for x less than 3 while another applies for x greater than or equal to 3, then 5 satisfies the second condition and you use only the second rule.
How should U.S. high school students practice SAT function notation?
The most effective approach is to practice each of the six function notation skill types separately before mixing them together in timed sessions. Start with basic evaluation to build confidence, then add expression inputs, then backward problems, then table and graph questions, then composition, and finally piecewise functions and real-world interpretation. For each skill, practice until the process feels automatic at any input type, including negative numbers and expressions. Use official College Board practice material from Tests 4 through 11 to confirm the skills work in the actual test format.
Does the Digital SAT test function domain and range?
Domain and range appear occasionally on the Digital SAT, but they are not among the most frequently tested function notation skills. When they do appear, the SAT typically asks about which x values are excluded from the domain of a rational function (where the denominator equals zero) or asks what the range of a function is given a specific domain restriction. Piecewise functions also implicitly test domain understanding since each rule only applies within its specified input interval.
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