Tolong di jawab nomor.8 y? bsok sikumpulkan

U1 = a
U2 = ar
U3 = ar^2
U.4 = ar^3
U5. = ar^4
U1 =a = 15
U3 = 135
135 = ar^2
135 = 15 r ^2
r^ 2 = 135 : 15
= 9
r = V9
r = 3
untuk U5 = 15 x 3^4
= 15 x 81
= 1215