jika g(x) = 2x -5 dan (f ° g) (x) = 6x - 13 maka f(3)

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

f(2x - 5) = 6x - 13
misal :
2x - 5 = a
x = (a + 5) / 2

f(a) = [6(a +5)/2] - 13
f(a) = 3(a+5) - 13
f(a) = 3a + 15 - 13
f(x) = 3x + 2

f(3) = 3.3 + 2 = 11