Jawabanmu

2014-02-21T04:51:14+07:00
U5=15 u8=120 u5=a.r^(5-1) =a.r^4 u8=a.r^(8-1) =a.r^7 u8/u5=(a.r^7)/(a.r^4) 120/15=r^3 8=r^3 r=2