Jawabanmu

2014-02-09T12:39:15+07:00
A.r=12
a.r^3=108
a.r.r^2=108
12.r^2=108
r^2=108/12
r^2=9
r=3 ,r>1 --->ar=12 , a=4
Un=a.r^n-1
Un=4.r^n-1

^ =pangkat