Jika (FoG) (x) = 4x^2 + 10x + 11 dan G(x) = 2x + 3, nilai F(x) ?

Diketahui:
g(x) = 2x + 3
(fog)(x) = 4x² + 10x + 11

misal:
2x + 3 = a
2x = a - 3
x = (a - 3)/2

(fog)(x) = 4x² + 10x + 11
f (g(x)) = 4x² + 10x + 11
f (2x + 3) = 4x² + 10x + 11

masukkan pemisalan tadi (subtitusi);

f (2x + 3) = 4x² + 10x + 11
f (a) = 4((a - 3)/2)² + 10((a - 3)/2) + 11
f (a) = 4((a² - 6a + 9)/4) + 5(a - 3) + 11
f (a) = a² - 6a + 9 + 5a - 15 + 11
f (a) = a² - a + 5
f (x) = x² - x + 5