PSAT Math Multiple-Choice Question 197: Answer and Explanation

Question: 197

The function f(x) is defined as f(x) = -3 g(x), where g(x) = x + 2. What is the value of f(5)?

• A. - 21
• B. - 1
• C. 4
• D. 7

Correct Answer: A

Explanation:

A

Difficulty: Easy

Category: Passport to Advanced Math/Functions

Getting to the Answer: When you see an expression like f(x), it means to substitute the given value for x in the function's equation. When there is more than one function involved, pay careful attention to which function should be evaluated first. You are looking for the value of f(x) at x = 5. Because f(x) is defined in terms of g(x), evaluate g(5) first by substituting 5 for x in the expression x + 2:

Therefore, (A) is correct.