Question

Tentukan rumus geometri
a. nilai suku ke n
b. jumlah suku ke n
dari
1. 27+9+3+.......
2.1,4,6,.........

Answer 1

27 + 9 + 3 + ...
a = 27
r = 9/27 = 1/3
a) Un = ar^(n - 1)
= 27(1/3)^(n - 1)

b) Sn = a(1 - r^n)/(1 - r)
= 27(1 - (1/3)^n)/(1 - 1/3)
= (81/2)(1 - (1/3)^n)