barisan geometri u3 = 16 u5 = 256 berapakah rasionya

u3 = a . r^2
16 = a . r^2

u5 = a . r^4
256 = a . r^4

256 = a . r^4
16. = a . r^2
------------------ :
16 = r^2
r = √16
r = 4