diketahui barisan geometri 3, 9, 27, ... Tentukan A) suku ke- n B) suku ke 5 C) jumlah 6 suku pertama
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Jawab:
Penjelasan dengan langkah-langkah:
3, 9, 27, ...
a = 3
r = 9/3 = 3
A. Uₙ = a . rⁿ ⁻ ¹
Uₙ = 3 . 3ⁿ ⁻ ¹
Uₙ = 3¹ ⁺ ⁿ ⁻ ¹
Uₙ = 3ⁿ
B. U₅ = 3⁵ = 243
C. Sₙ = [tex]\frac{a(r^{n-1}) }{r-1}[/tex]
S₆ = [tex]\frac{3(3^{6-1}) }{3-1}[/tex] = (3/2) (3⁵) = 729/2 = 364 [tex]\frac{1}{2}[/tex] = 364.5
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