Question

F(x) = 2x^2 - 5x - 15
g(x) = -2x - 1
find f(g(x)) ... somebody help me :(

Answer 1

f(g(x)) = 8x² + 18x - 8

Explanation:

Substitute x = g(x) into f(x) , that is

f(g(x))

= f(- 2x - 1)

= 2(- 2x - 1)² - 5(- 2x - 1) - 15

= 2(4x² + 4x + 1) + 10x + 5 - 15

= 8x² + 8x + 2 + 10x - 10

= 8x² + 18x - 8