Question

Tentukan rumus suku ke-n dari barisan geometri berikut :
a. 2,4,8,16,...
b. 3,-6,12,24,...
c. 3,9,27,81,...
d. 4,16,64,256,...
e. 1,1/4,1/16,1/64,...

tolong jawab secepatnya ya

Answer 1

A. a = 2, r = 2
Un = ar^(n-1)
= 2.2^(n-1)
= 2^(n-1+1) = 2^n
b. a = 3, r = 2
Un = ar^(n-1)
= 3.2^(n-1)
c. a = 3, r = 3
Un = ar^(n-1)
= 3.3^(n-1)
= 3^(n-1+1) = 3^n
d. a = 4, r = 4
Un = ar^(n-1)
= 4.4^(n-1)
= 4^(n-1+1) = 4^n = 2^(2n)
e. a = 1, r = ¼
Un = ar^(n-1)
= 1.¼^(n-1)
= 2^(-2)(n-1)
= 2^(2-2n)