Contoh
soal
Jabarkan
tiap binomial berikut ini.
a. (x + y)3
b. (x + 2y)4
Penyelesaian
= 3C0
∙ x3 – 0 y0 + 3C1
∙ x3 – 1 y1 + 3C2
∙ x3 – 2 y2 + 3C3
∙ x3 – 3 y3
= 1 ∙ x3 ∙ 1 + 3 ∙ x2 ∙ y +
3 ∙ x ∙ y2 + 1 ∙ x0 ∙ y3
= x3 + 3x2y + 3xy2 + 1 ∙ 1 ∙ y3
= x3 + 3x2y + 3xy2 + y3
= 4C0 ∙ x4 – 0 (2y)0 + 4C1
∙ x4 – 1 (2y)1 + 4C2
∙ x4 – 2 (2y)2
+ 4C3
∙ x4 – 3 (2y)3 + 4C4 ∙ x4 – 4 (2y)4
= 1 ∙ x4 + 4 ∙ x3 ∙ 2y
+ 6x2 ∙ 22 ∙ y2 +
4 ∙ x ∙ 23 ∙ y3 +
1 ∙
1 ∙ 24 ∙ y4
= x4 + 8x3y + 24x2y2 + 32xy3
+ 16y4
Contoh
soal
Tentukan
suku ke-4 dari (2x + 3y)6.
Penyelesaian
= 6C0⋅
(2x)6 – 0⋅ (3y)0 + 6C1⋅
(2x)6 – 1⋅ (3y)1 +
6C2⋅
(2x)6 – 2⋅ (3y)2 + 6C3⋅
(2x)6 – 3⋅ (3y)3 +
6C4⋅
(2x)6 – 4⋅ (3y)4 + 6C5⋅
(2x)6 – 5⋅ (3y)5 +
6C6⋅
(2x)6 – 6⋅ (3y)6
Jadi
suku ke-4 adalah = 6C3⋅
(2x)6 – 3⋅ (3y)3
= 6C3 ⋅
(2x)3 ⋅ (3y)3
Labels:
Matematika
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