Question

Given the functions f(x) = 2x + 5 and g(x) = x2 + 8, which of the following functions represents f(g(x)] correctly?

1. f[g(x)] = 4x2 + 20x + 32
2. f(g(x)] = 4x2 + 20x + 25
3. f[g(x)) = 2x2 + 16
4. f(g(x)) = 2x2 + 21

Answer 1

D

Explanation:

Took the test

Answer 2

Choice 4.

Explanation:

f(g(x))

Replace g(x) with x^2+8 since g(x)=x^2+8.

f(g(x))

f(x^2+8)

Replace old input,x, in f with new input, (x^2+8).

f(g(x))

f(x^2+8)

2(x^2+8)+5

Distribute:

f(g(x))

f(x^2+8)

2(x^2+8)+5

2x^2+16+5

Combine like terms:

f(g(x))

f(x^2+8)

2(x^2+8)+5

2x^2+16+5

2x^2+21