Diketatahui f(x)=x2-3x+5 dan g(x)=x+2 (fog) (x)=15 nilai x yang memenuhi adalah

f(g(x) = f(x + 2)
= (x + 2)^2 - 3(x + 2) + 5
= x^2 + 4x + 4 - 3x - 6 + 5
= x^2 + x + 3
(f o g)(x) = 15
x^2 + x + 3 = 15
x^2 + x - 12 = 0
(x - 3)(x + 4) = 0
x = 3 ; x = -4

Bab Fungsi
Matematika SMA Kelas XI

(fog) (x) = 15
(x + 2)² - 3 (x + 2) + 5 - 15 = 0
x² + 4x + 4 - 3x - 6 - 10 = 0
x² + x - 12 = 0
(x + 4) (x - 3) = 0
x = -4 atau x = 3