Dik : g(x) = X+9 (fog)(x) = ⅓(x²+6) Dit : f(x) = ……?

Anggap g(x) = y
fog(x) = f(g(x)) = 1/3 (y^2 + 6)
f(y) = 1/3 ((x+9)^2 +6)
f(x) = 1/3 (x^2 + 18x + 87)