Tentukan jumlah 6 suku pertama (s6) dari deret bilangan berikut... A. 4+12+36+... B. 8-16 +32-64+...

Sn = a(rⁿ - 1)/(r - 1)
a) a = 4
r = 12/4 = 3
S6 = 4(3^6 - 1) / (3-1)
= 4(729 - 1) / 2
= 2(728)
= 1456

b) a = 8
r = -16/ 8 = -2
S6 = 8(-2^6 - 1) / (-2-1)
= 8(64 - 1) / -3
= 8(63) / -3
= -168