Question f-x-27

2.1 Nonlinear Functions - Function composition and evaluation
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fx=2722x

The function f is defined by the given equation. If hx=fx-4, which of the following equations defines function h ?

A.

hx=172x

B.

hx=682x

C.

hx=27216x

D.

hx=2728x

f x = 272 2 x The function f is defined by the given equation. If

Hard-difficulty · SAT Math · Nonlinear Functions — Function composition and evaluation. Read the question above, select your answer, and check the full explanation below to understand exactly why the correct choice works.

Answer explanation

Choice A is correct. It's given that f(x)=272(2)x and h(x)=f(x-4). Substituting x - 4 for x in f(x)=272(2)x yields fx-4=2722x-4. Substituting hx for fx-4 in this equation yields hx=2722x-4. Using the properties of exponents, the function h(x)=272(2)x-4 can be rewritten as hx=2722x24, which is equivalent to hx=2722x16, or h(x)=17(2)x. Therefore, of the given choices, an equation that defines function h is h(x)=17(2)x.

Choice B is incorrect. This equation defines function h if h(x)=f(x-2), not h(x)=f(x-4).

Choice C is incorrect. This equation defines function h if h(x)=f(4x), not h(x)=f(x-4).

Choice D is incorrect and may result from conceptual or calculation errors.