Question

(03.07 LC)

Find the sum of the first five terms of the geometric series 8, -24, 72, ...
O a
b
Oc
C
O d
484
488
648
684

Answer 1

S₅ = 648

Explanation:

the sum to n terms of a geometric series is

`S_(n)` = a₁
`(r)^(n-1)`

a₁ is the first term , r the common ratio , n the term number

given

8 , - 24 , 72

with a₁ = 8 and r =
`(a_(2) )/(a_(1) )` =
`(-24)/(8)` = - 3 , then

S₅ = 8
`(-3)^(4)` = 8 × 81 = 648