Tentukan 5 suku pertama barisan berikut…?​

Jawab:

nomor 1

Un = 3n + 7

n = 1 —> U₁ = 3(1) + 7 = 3 + 7 = 10

n = 2 —> U₂ = 3(2) + 7 = 6 + 7 = 13

n = 3 —> U₃ = 3(3) + 7 = 9 + 7 = 16

n = 4 —> U₄ = 3(4) + 7 = 12 + 7 = 19

n = 5 —> U₅ = 3(5) + 7 = 15 + 7 = 22

Jadi, lima suku pertama adalah 10, 13, 16, 19, dan 22.

nomor 2

Un = 1/2 n² + 4

n = 1 —> U₁ = 1/2(1)² + 4 = 1/2 + 4 = 4,5

n = 2 —> U₂ = 1/2(2)² + 4 = 2 + 4 = 6

n = 3 —> U₃ = 1/2(3)² + 4 = 4,5 + 4 = 8,5

n = 4 —> U₄ = 1/2(4)² + 4 = 8 + 4 = 12

n = 5 —> U₅ = 1/2(5)² + 4 = 12,5 + 4 = 16,5

Jadi, lima suku pertama adalah 4,5 ; 6; 8,5 ; 12 dan 16,5.

nomor 3

Un = 3n²

n = 1 —> U₁ = 3(1)² = 3

n = 2 —> U₂ = 3(2)² = 12

n = 3 —> U₃ = 3(3)² = 27

n = 4 —> U₄ = 3(4)² = 48

n = 5 —> U₅ = 3(5)² = 75

Jadi, lima suku pertama adalah 3,12, 27, 48, dan 75.

nomor 4

Un = n(n² + 2)

n = 1 —> U₁ = 1(1²+ 2) = 1(3) = 3

n = 2 —> U₂ = 2(2² + 2) = 2(6) = 12

n = 3 —> U₃ = 3(3² + 2) = 3(11) = 33

n = 4 —> U₄ = 4(4² + 2) = 4(18) = 72

n = 5 —> U₅ = 5(5² + 2) = 5(27) = 135

Jadi, lima suku pertama adalah 3, 12, 33, 72, dan 135.

semoga membantu

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