Every attempt I've made to complete composite functions i've done wrong. Can anyone help me?

Question

Let f (x) = 3x2+ 7 and g(x) = x – 4.

 

(a) Find the composite function ) ( f o g)(x and simplify. 
(b) Find ( f o g)(− )1 . 

Answer 1

f(x) = 3x² + 7

g(x) = (x - 4)

 

(f o g)(x) = 3(x - 4)² + 7

(f o g)(x) = 3(x² - 8x + 16) + 7

(f o g)(x) = 3x² - 24x + 48 + 7

(f o g)(x) = 3x² - 24x + 55