Pada suatu barisan geometri diketahui s2 =6 dan s4= 30. Hitunglah suku ke - 10 dari barisan geometri tersebut

Sn = a ( r^n - 1) / (r-1)
S2 = a (r^2 - 1) / (r - 1)
6 = a ( r^2 - 1) / (r-1)
6( r-1) = a (r^2 - 1)
(r -1 ) = a ( r^2 - 1)/6. (1)
S4 = a ( r^4 - 1 ) / (r-1)
30 = a ( r^4 - 1) / (r-1)
(r -1) = a (r^4 -1)/30...(2)
a ( r^2 - 1)/6 = a ( r^4 -1)/30
5a ( r^2 - 1) = a ( r^4 - 1)
5 ( r^2 - 1) = (r^4 - 1)
5 ( r^2 - 1 ) = (r^2 - 1) (r^2 + 1)
r^2 + 1 = 5
r^2 = 5-1
r^2 = 4
r^2 = 2^2
r = 2
dari 6 = a ( r^2 - 1) / (r-1)
a (2^2 -1) / (2-1) = 6
a ( 3)/1 = 6
3a = 6
a = 6/3 = 2
Un = ar^(n-1)
U10 = 2(2^9)
= 2^10
= 1024