1. Diketahui f(x) = 3x + 2 dan g(x) = 2 – x. Rumus fungsi (f o g)(x) =....
Pembahasan: (f o g)(x) = f(g(x))
= f (2 − x)
= 3(2 − x) + 2
= 6 − 3x + 2
= −3x + 8
= f (2 − x)
= 3(2 − x) + 2
= 6 − 3x + 2
= −3x + 8
Pembahasan: (g o f)(x) = g(f(x))
= g(3x-4)
= 2(3x-4)
=
2(3x-4)
= 6x-8
3. Jika f(x) = 2x + 3 dan
(f o g) = 2x2 + 6x – 7, maka g(x) =....
Pembahasan:
(f o g)(x) = 2x2 + 6x – 7
f(g(x)) = 2x2 + 6x – 7
2(g(x)) + 3 = 2x2 +
6x – 7
2 (g(x)) = 2x2 + 6x –7– 3
2 (g(x)) = 2x2 + 6x –10
g(x) = x2 +
3x – 5
4.
Diketahui fungsi f(x) = 3x − 1 dan g(x) = 2x2 + 3. Nilai dari komposisi fungsi
(g
f)(1) =....
Pembahasan:
(g o f)(x) = g(f(x))
(g
o f)(x) = g(3x − 1)
(g o f)(x) = 2(3x − 1)2 + 3
(g o
f)(x) = 2(9x2 − 6x +
1) + 3
(g
o f)(x) = 18x2 − 12x +
2 + 3
(g o f)(x) = 18x2 − 12x + 5
(g o f)(x) = 18x2 − 12x + 5
(g
o f)(1) = 18(1)2 −
12(1) + 5 = 11
5. Jika
f(x) = x2 + 3x dan g(x) = x – 12, maka nilai (f o g)(8) = ....
Pembahasan:
a.
Menentukan nilai fungsi g(8)
g(x) =
x – 12
g(8) = 8 – 12 = – 4
= f(–4)
=
(–4)2 + 3(–4)
= 16 – 12 = 4
6. Jika f(x) = 3x2 + 4x + 1 dan g(x) = 6x. Tentukan nilai fungsi (f o g)(2) =....
Pembahasan:
a.
Menentukan nilai fungsi (f o g)(x)
(f o g)(x) = f(g(x))
(f o g)(x) = f(g(x))
(f o g)(x) = f(6x)
(f o g)(x) = 3(6x)2 + 4(6x) + 1
(f o g)(x) = 3(6x)2 + 4(6x) + 1
(f
o g)(x) = 3(36x2) +
24x + 1
(f o g)(x) = 108x2 + 24x + 1
(f o g)(x) = 108x2 + 24x + 1
b.
Menentukan nilai fungsi (f o g)(2)
(f o g)(x) = 108x2 + 24x + 1
(f o g)(2) = 108(2)2 + 24(2) + 1
(f o g)(2) = 432 + 28 + 1 = 461
(f o g)(x) = 108x2 + 24x + 1
(f o g)(2) = 108(2)2 + 24(2) + 1
(f o g)(2) = 432 + 28 + 1 = 461
7. Diketahui g(x) = x – 2 dan (f o g)(x) = 3x – 1.
Tentukan rumus fungsi f(x) =....
Pembahasan:
a.
x dimisalkan dengan m
x
– 2 = m
x = m + 2
b.
(f o g)(x)
= 3x – 1
f(g(x)) = 3x – 1
f(x – 2) = 3x – 1
f(m) = 3x – 1
f(m) = 3(m + 2) – 1
f(m) = 3m + 6 – 1
f(m) = 3m + 5
f(x) = 3x + 5
8. Diketahui f(x) = –2x + 3 dan g(x) = x2 – 4x + 5. Rumus fumgsi f o g (x) dan g o f(x) =...
9. Diketahui f(x) = 3x + 5. jika x = 2 tentukan nilai f(x + 4)
+ f(2x) + f(x2) =....
Pembahasan:
f o g (x) = f(g(x))
f o g (x) = f(x2 – 4x + 5)
f o g
(x) = –2(x2 – 4x + 5) + 3
f o g
(x) = –2x2 + 8x –10 + 3
f o g (x) = –2x2 + 8x –7
g o f(x) = g(f(x))
g o f(x) = g(2x + 3)
g o f(x) = (2x + 3)2 – 4(–2x + 3) + 5
g o f(x) = (4x2 – 12x +
9) + 8x – 12 + 5
g o f(x) = 4x2 – 4x + 2
g o f(x) = 4x2 – 4x + 2
Pembahasan:
10.
Diketahui g(x) = x2 + 3x + 2 dan (f o
g)(x) = 4x2 + 12x + 13.
Tentukan rumus f(x)=....
f(x + 4) + f(2x) + f(x2)
= f(2 + 4) + f(2(2)) + f(22)
f(x + 4) + f(2x) + f(x2)
= f(6) + f(4) + f(4)
f(x + 4) + f(2x) + f(x2)
= (3(6) + 5) + (3(4) + 5) + 3(4) + 5
f(x + 4) + f(2x) + f(x2)
= 23 + 17 + 17
f(x + 4) + f(2x) + f(x2)
= 57
Pembahasan:
a.
Pemisalan
x2 + 3x + 2 = a
x2 + 3x = a – 2
b.
(f o g)(x) = 4x2 + 12x + 13
f(g(x)) = 4x2 + 12x + 13
f(x2 + 3x + 2) = 4x2 + 12x + 13
f(a) = 4x2
+ 12x + 13
f(a) = 4(x2 + 3x) + 13
f(a) = 4(a – 2) + 13
f(a) = 4a – 8 + 13
f(a) = 4a + 5
f(x) = 4x + 5