Pada suatu barisan geometri, diketahui U subscript 1 plus U subscript 3 equals 70 dan U subscript 2 plus U subscript 4 equals 210. Rasio barisan geometri tersebut adalah
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Jawab:
Penjelasan dengan langkah-langkah:
U1 + U3 = 70
U2 + U4 = 210
r = ...?
U1 = a
Un = a.r^(n - 1)
U1 + U3 = 70
a + ar² = 70
a (1 + r²) = 70
a = 70/(1 + r²)
U2 + U4 = 210
ar + ar³ = 210
ar (1 + r²) = 210
(70/(1 + r²)).r(1 + r²) = 210
70r = 210
r = 210/70
r = 3
Rasionya adalah 3.