2.Tentukan (fog)(x) untuk x=-2 apabila f(x)=x²-4x-5 dan g(x) = 15 / x+3
1. Diketahui f(x)= x²-2x-8 dan g(x) = x²+3x+2. Tentukan f(-1) dan (gof)(-1)
1)
f (x) = x² – 2x – 8
g (x) = x² + 3x + 2
f (-1) = (-1)² – 2.(-1) – 8
= 1 + 2 – 8
= -5
gof (-1) = g (f (-1))
= g (-5)
= (-5)² + 3.(-5) + 2
= 25 – 15 + 2
= 12
2)
f(x)=x² – 4x – 5
g(x) = 15 / (x + 3)
fog (-2) = f (g(-2))
= f (15 / (-2 + 3))
= f (15)
= 15² – 4.15 – 5
= 225 – 60 – 5
= 160
1) f(x) = x² – 2x – 8
f(-1) = (-1)² – 2(-1) – 8 = 1 + 2 – 8 = -5
g(x) = x² + 3x + 2
(g o f)(-1) = g(f(-1)) = g(-5) = (-5)² + 3(-5) + 2 = 25 – 15 + 2 = 12
2) g(x) = 15/(x + 3)
=> g(-2) = 15/(-2 + 3) = 15/1 = 15
f(x) = x² – 4x – 5
(f o g)(x) untuk x = -2
(f o g)(-2) = f(g(-2)) = f(15) = 15² – 4(15) – 5 = 225 – 60 – 5 = 160