Question

Find the sum of the first nine terms of the geometric series 8, −24, 72, … −19,6893 19,691 39,368 52,488

plz explain and hurry

Answer 1

A: 39,368

Explanation:

I took the quiz on FLVS and got it right!

Answer 2

39,368

Explanation:

The sum of n terms of a geometric sequence is

`S_(n)` =
`(a(r^n-1))/(r-1)`

where a is the first term and r the common ratio

r = - 24 ÷ 8 = - 3 and a = 8, thus

`S_(9)` =
`(8[(-3)^9-1)/(-3-1)` =
`(8[-19683-1])/(-4)` =
`(8(-19684))/(-4)` =
`(-157472)/(-4)` = 39368