Jawabanmu

2014-04-29T00:53:22+07:00
A = 125 = 5^3
r = 25/125=1/5 = 5^-1

Un = ar^(n-1)
Un=ar^n.r^-1
Un=5^3 . (5^-1)^n . (5^-1)^-1
Un= 5^3 . 5^-n . 5
Un=5^4.5^-n
Un=5^(4-n)