GRE-Style: Function Evaluation

GRE Quantitative · Axiom Academy

EXAMPLE GRE-Style: Function Evaluation Evaluating a quadratic function at two inputs — including a negative one — and comparing the results. Let f(x) = x^2 - 3x + 5 . Quantity A is f(4) . Quantity B is f(-2) . Which quantity is greater? Nice work — you evaluated a function at two different inputs and used the results to answer a GRE-style quantitative comparison. Substitute carefully: f(a) means replace every x in the rule with a , then simplify with order of operations. Watch the negative input: (-2)^2 = 4 , not -4 — squaring a negative always gives a positive, and a -3x term becomes -3(-2) = +6 . Result: f(4) = 9 and f(-2) = 15 , so f(4) < f(-2) — Quantity B is greater. On the GRE, quantitative-comparison questions built from function evaluation almost always hinge on a sign slip at a negative input — plug in one term at a time and you won't get tripped up.

This is the written version of the interactive lesson above. See the full GRE Quantitative course.