tentukam suku ke 7 dari barisan geometri berikut , A.3,12,48,....... B. 243,81,27,....... C. 10,20,40,......

A. 3, 12, 48, ...
a= 3 ; r = 12/3 = 4
Un= ar^n-1
U7 = 3.4^7-1
U7 = 3.4^6 = 3 × 4096 = 12288

B. 243, 81, 27, ...
a = 243 ; r = 81/243 = 1/3
Un = ar^n-1
U7 = 243.1/3^7-1
U7 = 243.1/3^6 = 243.1/729 = 1/3

C. 10, 20, 40, ...
a = 10 ; r = 20/10 =2
Un = ar^n-1
U7 = 10.2^7-1
U7 = 10.2^6 = 10 × 64 = 640