Tolong ya..

U3 = a.r^n-1
1250 = a.r^2 ….. (i)

U6 = a.r^n-1
156250 = a.r^5 ….. (ii)

a.r^5 = 156250
a.r^2 = 1250
———————– /
r^3 = 125
r = 5
Maka, a = 50

U8 = 50 x 5^7
     = 3906250

3906250 banyak kali jawabanya