Question

Let f(x) = -2x - 7 and g(x) = -4x + 6. Find (f o g)(-5)

A. –6
B. 3
C. 26
D. –59

Answer 1

Option D. -59 is the correct answer.

Explanation:

The given function in the question are f(x) = -2x - 7 and g(x) = -4x + 6

Then we have to find the value of (f o g)(-5).

So we will find the function (f o g)(x) first.

(f o g)(x) = -2(-4x + 6) - 7 = 8x - 12 - 7

= 8x - 19

Now (f o g)(-5) = 8×(-5) - 19 = -(40 + 19) = -59

Therefore the value of (f o g)(-5) = -59.

Option D is the correct answer.

Answer 2

Option D. - 59

Explanation:

To solve this problem the first step is to introduce the function g(x) inside the function f(x). Therefore the range of g(x) will now be the domain of f(x).

f(x) = -2x - 7

g(x) = -4x + 6

(f o g)(x) = f(g(x))

f(g(x)) = -2(-4x + 6) - 7

f(g(x)) = 8x -12 -7

f(g(x)) = 8x -19

Now we make x = -5

(f o g)(- 5) = 8 (-5) -19

(f o g)(- 5) = -59

The correct option is D. -59