Diket (f•g)(x) = 4x²-4x-5 tentukan f(x) jika g(x) = 2x + 1

(fog) (x) = 4x²-4x-5
f(g(x) = 4x²-4x-5
f(2x+1)= 4x²-4x-5
misal
t = 2x+1
2x = t-1
x = t-1 / 2
f(x) = 4(t-1 / 2)²-4(t-1 / 2) - 5
= 2(t-1)² - 2(t-1)-5
= 2(t²-2t+1) - 2t+2-5
= 2t²-6t-1
f(x) = 2x²-6x-1