Question f-x-x-

2.1 Nonlinear Functions - Function composition and evaluation
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f(x)=(x+6)(x+5)(x-4)

The function f is given. Which table of values represents y=f(x)-3?

A.
x y
-6 -9
-5 -8
4 1
B.
x y
-6 -3
-5 -3
4 -3
C.
x y
-6 -3
-5 -2
4 7
D.
x y
-6 3
-5 3
4 3

f ( x ) = ( x + 6 ) ( x + 5 ) (

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 B is correct. It’s given that fx=(x+6)(x+5)(x-4) and y=f(x)-3. Substituting (x+6)(x+5)(x-4) for fx in the equation y=f(x)-3 yields y=(x+6)(x+5)(x-4)-3. Substituting -6 for x in this equation yields y=(-6+6)(-6+5)(-6-4)-3, or y = -3 . Substituting -5 for x in the equation y=(x+6)(x+5)(x-4)-3 yields y=(-5+6)(-5+5)(-5-4)-3, or y = -3 . Substituting 4 for x in the equation y=(x+6)(x+5)(x-4)-3 yields y=(4+6)(4+5)(4-4)-3, or y = -3 . Therefore, when x = -6 then y = -3 , when x = -5 then y = -3 , and when x = 4 then y = -3 . Thus, the table of values in choice B represents y=f(x)-3.

Choice A is incorrect. This table represents y = x - 3 rather than y=f(x)-3.

Choice C is incorrect. This table represents y = x + 3 rather than y=f(x)-3.

Choice D is incorrect. This table represents y=fx+3 rather than y=f(x)-3.