berapa jumlah 6 suku pertama pada barisan geometri 6+3+

6+ 3 +...

U1 = a= 6
r = U2/U1= 3/6 = 1/2
n = 6

Jumlah 6 suku pertama
S6 = a (1 - r^n) / (1 - r)
S6 = 6 (1 - (1/2)⁶) / (1 - 1/2)
S6 = 6 (1 - (1/64)) / (1/2)
S6 = 6 ((64 - 1) / 64) / (1/2)
S6 = 6 (63/64) / (1/2)
S6 = (378/64) x 2/1
S6 = 378/32
S6 = 11,8125

a = 6
r = U2/U1 = 3/6 = 1/2
dit S6
Sn = a(1 - r^n) / (1-r)
S6 = 6(1 - (1/2)^6) / (1 - 1/2)
= 6 ( 1 - 1/64) / (1/2)
= 6(63/64) / (1/2)
= 6 x 63/64 x 2/1
= 189 / 13 atau 11,8125