The function f is defined by f(x) = 7 - 2x. What is the value... | SAT Linear functions Question, Answer Explained

Math · AlgebraEasy

The function $f$ is defined by $f(x) = 7 - 2x$ . What is the value of $f(-3)$ ?

$-15$

$1$

$10$

$13$

Show answer and explanation

Answer: D

Substitute $-3$ for $x$ : $f(-3) = 7 - 2(-3) = 7 + 6 = 13$ .

Choice B treats $-2(-3)$ as $-6$ , but the product of two negative numbers is positive.

Why the other choices are wrong

A. This multiplies 7 - 2 by -3. Multiply -2 by -3 first, then add the result to 7.
B. This treats -2 times -3 as -6. The product of two negatives is positive.
C. This adds 3 to 7 and leaves out the factor of 2.

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