19. Diketahui f(x)=5-x dan g(x)=2x+3.Nilai (g. f)^-1=(-5)
12. Jika f(x) = x + 3 dan (g. f)(x) = x^2+ 2x – 5,fungsi g(x)
Diketahui:
f(x) = x + 3
(g°f)(x) = x² + 2x – 5
Ditanyakan:
(g)(x) = —-?
Penyelesaian:
(gºf)(x) = x² + 2x – 5
g(f(x)) = x² + 2x – 5
g(x + 3) = x² + 2x – 5
g(x) = (x – 3)² + 2(x – 3) – 5
g(x) = x² – 6x + 9 + 2x – 6 – 5
g(x) = x² – 4x – 2