Fungsi f: R ➙ R dan g: R ➙ R dinyatakan oleh f(x) = x² – 2x + 4 dan g(x) = 3 – x. Nilai komposisi fungsi (g ⚬ f)(2) yakni ….
Jawab:
f(x) = x² – 2x + 4 dan g(x) = 3 – x
(g ⚬ f)(x) = g(f(x)) = g(x² – 2x + 4)
= 3 – (x² – 2x + 4)
= 3 – x² + 2x – 4
= -x² + 2x – 1
Untuk x = 2 diperoleh:
(g ⚬ f)(2) = -(2)² + 2(2) – 1 = -4 + 4 – 1 = -1
Cara lain:
(g ⚬ f)(2) = g(f(2)) = g(2² – 2(2) + 4)
= g(4) = 3 – 4 = -1
Makara, (g ⚬ f)(2) = -1.