suatu barisan geometri suku ke 3 dan ke 5 berturut-turut

Dik. barisan deret geometri :
U3 = 18 & U5 = 162
Dit. suku ke-9 (U9)?

Jawab...

U5 = a × r^4 = 162
U3 = a × r^2 = 18
-------------------- (:)
@ r^2 = 9
@ r = 3

a :
a × r^2 = 18
a × (3)^2 = 18
a × 9 = 18
a = 18/9
a = 2

U9 = a × r^8
U9 = 2 × (3)^8
U9 = 2 × 6561
U9 = 13122 (A)

Semoga membantu.. ^_^