SAT Math Multiple Choice Question 590: Answer and Explanation

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Test Information

Question: 590

5. If f(x) = 3x + 5, what is f(6) – f(2)?

  • A. 11
  • B. 12
  • C. 17
  • D. 23

Correct Answer: B

Explanation:

B

Difficulty: Medium

Category: Passport to Advanced Math / Functions

Strategic Advice: When evaluating a function, substitute the value inside the parentheses for x in the equation.

Getting to the Answer: Evaluate the function at x = 6 and at x = 2, and then subtract the second output from the first. Note that this is not the same as first subtracting 6 – 2 and then evaluating the function at x = 4.

f(6) = 3(6) + 5 = 18 + 5 = 23

f(2) = 3(2) + 5 = 6 + 5 = 11

f(6) – f(2) = 23 – 11 = 12

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