Jika f(x)=x-2 dan (g ○ f)(x)=2x2-1. Maka rumus g(x) adalah

g(f(x)) = 2x^2 - 1
g(x-2) = 2x^2 - 1

misal
x-2 = p
x = p+2
maka:
g(p) = 2(p+2)^2 - 1
g(p) = 2(p^2+4p+4) -1
g(p) = 2p^2 +8p+8-1
g(p) = 2p^2 +8p +7
g(x) = 2x^2 +8x+7