jika diketahui g(x)=3x-2 dan (f•g)(x) =12x²-6x+5 maka tentukan fungsi f(x)

Misal
3x - 2 = a
x = (a + 2)/3

(f ○ g)(x) = 12x^2 - 6x + 5
f(g(x)) = 12x^2 - 6x + 5
f(3x - 2) = 12x^2 - 6x + 5
f(a) = 12((a + 2)/3)^2 - 6((a + 2)/3) + 5
f(a) = 12((a^2 + 4a + 4)/9) - 2(a + 2) + 5
f(a) = (4a^2 + 16a + 16)/3 - 2a - 2 + 5
f(a) = (4a^2 + 16a + 16)/3 - 2a + 3
f(a) = (4a^2 + 16a + 16)/3 - 6a/3 + 9/3
f(a) = (4a^2 + 10a + 25)/3
f(x) = (4x^2 + 10x + 25)/3