Question

Hitunglah jumlah sampai 8 suku dari deret geometri:
a. 1-1+1-1+....
b.
c. 12-6+3-1,5+....
d.

rumusnya:
1. , r<1
2.

Answer 1

A. r = U2/U1 = -1/1 = 1 (r < 1)
   S8 = a(1 - r^8) / (1 - r ) = 1 (1 - (-1)^8) / ( 1 - (-1)) = 1 ( 1 - 1) / (2 ) = 0 / 2 = 0
b. r = U2 / U1 = 2/3 / 2 = 2 / 6 = 1/ 3
   S8 = a (1 - r^8) / (1 - r ) = 2 ( 1 - (1/3)^8) / ( 1 - (1/3) = 2 ( 1 - 1/6561 ) / ( 2/ 3) = 19680/6561
c. r = -1/2
  S8 = 1020/128
d. r = 2
   S8 = 255/16