The function f is defined by f(x) = 2x^2 - 5x. What is the... | SAT Nonlinear functions Question, Answer Explained

Math · Advanced MathEasy

The function $f$ is defined by $f(x) = 2x^2 - 5x$ . What is the value of $f(-3)$ ?

$-3$

$3$

$33$

$51$

Show answer and explanation

Answer: C

Substitute $-3$ for $x$ : $f(-3) = 2(-3)^2 - 5(-3) = 2(9) + 15 = 18 + 15 = 33$ .

Choice B treats $-5(-3)$ as $-15$ , but the product of two negative numbers is positive.

Why the other choices are wrong

A. This treats (-3)² as -9, which gives -18 + 15. Squaring -3 gives 9.
B. This treats -5 times -3 as -15. The product of two negatives is positive, so add 15.
D. This squares the 2 along with the -3, computing (2 × -3)² = 36 instead of 2 × 9 = 18.

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