Jika g(x) =2x-5 dan (f•g) (x) = 6x-13 maka f(3)

(fog) (x) = 6x - 13
f(g(x))= 6x - 13
f(2x-5)= 6x - 13

misal t = 2x-5
2x = t+5
x = t+5 / 2

f(x) = 6(t+5 / 2) - 13
= 3(t+5) - 13
= 3t+15 - 13
= 3t+2
atau
f(x) = 3x + 2

f(3)= 3(3)+2=9+2=11