tentukan banyak suku untuk setiap barisan geometri a.5,10,20,...,1.280 b.-128,64,-32,...,1/16

Baris Geometri
a). 5,10,20,...,1280
r = U2/U1 = 10/5 = 2
Un = ar^n-1
1280 = 5(2)^n-1
256 = 2^n x 1/2
2^n = 512
n = 9

b). -128,64,-32,...,1/16
r = U2/U1
= 64/-128 = -1/2
Un = ar^n-1
1/16 = -128(-1/2)^n-1
n = -4

maaf kalo salah ya