f(x) = xkuadrat -4 , g(x) = 2x-6 ,(fog)(x) = 4,maka nilai x?

(fog) (x) = f(g(x))
= (g(x))²-4
= (2x-6)²-4

(fog)(x)= 4
(2x-6)² - 4 = 4
4x²-24x+36-4=4
4x²-24x-28=0 bagi 4
x²-6x-7=0
(x-7)(x+1)
jadi x= 7 atau x=-1