Question

Suatu barisan geometri diketahui suku ke 2 = 6 dan suku ke5=3/4 .suku pertama dan rasio barisan tersebut adalah

Answer 1

Deret geometri
u5/u2 = r^4 / r
3/4 /6 = r^3
1/8 = r^3
r = 1/2

u2 = a . r
6 = a . 1/2
a = 12

Answer 2

Un = ar^n-1
U2 = ar = 6  => a = 6/r

U5 = ar^4 = 3/4
(6/r) r^4 = 3/4
6r^3 = 3/4
r^3 = 3/24
r^3 = 1/8
r = ∛1/8
r = 1/2

a = 6/r = 6 / 1/2 = 12