GRE® Quant Practice | Algebra Q4

The GRE maths sample question given below is a select one or more answers type question in Algebra. Computing values of Functions is the concept tested in the question. A medium difficulty GRE Quantitative Reasoning practice question.

Question 4 : If f(x) = x² + 4, which of the following is equal to f(9)?
Indicate ALL such answers.

1. f(13)
2. f(-3)
3. f(-9)
4. f(f(√5))
5. f(f(√13))
6. f(f(-√5))

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Video Explanation

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Explanatory Answer | GRE Functions Practice

Step 1 of solving this GRE Functions Question: Compute the value of f(9)

f(x) = x² + 4
f(9) = 9² + 4 = 85

Step 2 of solving this GRE Functions Question: Compute values for each answer option

Option A: f(3) = 3² + 4 = 13.
13 is not equal to f(9).
Hence, this option is not an answer.

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Option B: f(13) = 13² + 4 = 173
173 is not equal to f(9).
Hence, this option is not an answer.

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Option C: f(-9) = (-9)² + 4 = 85
85 is equal to f(9).
Hence, this option is one of the right answers.

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Option D: f(f(√5)) = f((√5)² + 4) = f(9) = 85
85 is equal to f(9).
Hence, this option is one of the right answers.

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Option E: f(f(√13)) = f((√13)² + 4) = f(17) = 17² + 4 = 293
293 is not equal to f(9).
Hence, this option is not an answer.

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Option F: f(f(-√5)) = f((-√5)² + 4) = f(9) = 85
85 is equal to f(9).
Hence, this option is one of the right answers.

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Choice C, D, and F are the correct answers