Jika g(x) = x2-1 dan fungsi memenuhi (f o g) (x) = x4 maka f(4) =

(f○g) (x) = 4x
f (g(x)) = 4x
f (2x-1) = 4x

misal,
2x-1 = p
2x = p+1
x = p+1 / 2

f (2 (p+1 /2 ) -1 = 4 (p+1 / 2)
f (p+1-1) = 2p+2
f (p) = 2p+2

f (x) = 2x + 2

maka,
f (4) = 2(4)+2
=8+2
=10