ada yg tau caranya? udh dicari cari tp gak dapet -.

a=4
U5=324
a x r^4 = 324
4 x r^4 = 324
r^4 = 81
r=3
Sn=[a(r^n-1)]/(r-1)
S5=[4(243-1)]/(3-1)
S5=(4x242)/2
S5=968/2=484 cm ....... (b)

Geometri ,
a = 4
U5 = ar^4 = 324

U5/a = ar^4/a = 324/4
r^4 = 81
r = 3

Dit. S5
Sn = a((r^n)- 1) / r - 1
= 4 ( (3^5) - 1) / 3-1
= 4 ( 243 - 1)/2
= 2 . 242
= 484 cm (b.)