jika g(x) = x- 4 dan (fog) (x) = x kuadrat - 5x + 2 fungsi f(x)

(f o g)(x) = x^2 - 5x + 2
f(g(x)) = x^2 - 5x + 2
f(x - 4) = x^2 - 5x + 2
Misal : x - 4 = a => x = a + 4
f(a) = (a + 4)^2 - 5(a + 4) + 2
f(a) = a^2 + 8a + 16 - 5a - 20 + 2
f(a) = a^2 + 3a - 2
f(x) = x^2 + 3x - 2