Diketahui deret geometri 2 + 1 + 1/2, 1/4 ..... tentukan jumlah 15 suku pertamanya

jawab

a = 2
r = 1/2

s15 = a (1 - r^15) / ( 1-  r)
s15 = 2 (1 - 1/2^(15) / ( 1- 1/2)
s15 = 4 (1) = 4