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

(f•g)(x) = f(g(x))

(f•g•g invers(x)) = f(x)
(f(g(g invers(x))) = f(x)

kita cari (g invers(x)) dahulu
y = 2x + 1
y - 1 = 2x
(y - 1)/2 = x

g invers(x) = (x-1)/2

f(x) = f(g(g invers(x)))
f(x) = (4((x-1)/2)²) - 4((x-1)/2) - 5
f(x) = (4(x-1)²/2²) - 2(x-1) - 5
f(x) = (4(x² - 2x + 1)/4) - 2x + 2 - 5
f(x) = x² - 2x + 1 - 2x - 3
f(x) = x² - 4x - 2

semoga membantu