1. jika f(x) = 2x^2+5x dan g(x) = 1/x tentukan (f o g)(2)?

1.
f(x) = 2x^2+5x
g(x) = 1/x
(f o g)(2)
= f(g(2))
= f(1/2)
= 2(1/2)² + 5(1/2)
= 2(1/4) + 5/2
= 1/2 + 5/2
= 6/2
= 3

2.
f(x) = 2x+5
g(x) = x-1/x+4
(f o g)(a) =5
f(g(a)) = 5
f((a – 1)/(a + 4)) = 5
2(a – 1)/(a + 4) = 5
2(a – 1) = 5(a + 4)
2a – 2 = 5a + 20
2a – 5a = 20 + 2
-3a = 22
a = -22/3

3.
f(x) = 2x²+3x-5
g(x) = 3x-2
(g o f)(a) = -11
g(f(a)) = -11
g(2x² + 3x – 5) = -11
3(2x² + 3x – 5) – 2 = -11
3(2x² + 3x – 5) = -11 + 2
3(2x² + 3x – 5) = -9
2x² + 3x – 5 = -9/3
2x² + 3x – 5 = -3
2x² + 3x – 5 + 3 = 0
2x² + 3x – 2 = 0
(x + 1)(2x – 1) = 0
x = -1 atau x = 1/2

4.
f(x) = 3x+2
g(x) =2-x
(g o f) (x)
= g(f(x))
= g(3x + 2)
= 2 – (3x + 2)
= 2 – 3x – 2
= -3x