suatu barisan u3=9 dan u6=243 tentukan u5

u(3) = a x r^2 = 9
u(6) = a x r^5 = 243
----------------------------(dibagi)
r^-3 = 27^-1
r^3 = 27
r = 3

a x r^2 = 9
a x 3^2 = 9
a = 9/9
a = 1

u(5) = 1 x 3^4 = 1 x 81 = 81