SAT Math Multiple Choice Practice Question 511: Answer and Explanation

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Question: 511

10. If f(g(a)) = 6, f(x) = + 2, and g(x) = |x2 - 10|, which of the following is a possible value of a?

A.
B.
C. 2
D. 6
E. 18

Correct Answer: A

Explanation:

A This a great opportunity to Plug In The Answers! Start with C, and plug into g(x) first: |22 – 10| = 6. Now plug that value into f(x): + 2 = 5. Cross out C. Now the tough decision is whether or not a bigger or smaller value of a is needed. If you aren't sure which way to go, then just try another answer. For instance, plug D into g(x): |62 – 10| = 26. Now into f(x): + 2 = 15. You got a lot further away from the answer, and using D resulted in a number much too big! Cross out E as well, and try one of the first two answers. Plug A into g(x): . Now into f(x): + 2 = 6! A is the correct answer.

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