Question

Find s8 for the following geometric sequence: 3, –6, 12, –24.

Answer 1

Find s8 for the following geometric sequence: 3, –6, 12, –24. = –255

Answer 2

`S_(8)` =
`-255)`.

Explanation:

Given : geometric sequence: 3, –6, 12, –24.

To find : Find s8 for the following geometric .

Solution : We have given geometric sequence: 3, –6, 12, –24.

Where, first term = 3, common ration :
`(-6)/(3)` = -2.

Formula used :
`a((1-r^(n))/(1-r) )`

Where, a = first term , r = common ratio.

`S_(8)` =
`3((1-(-2)^(8))/(1-(-2)) )`.

`S_(8)` =
`3((1- 256)/(1+2) )`.

`S_(8)` =
`3((-255)/(3) )`.

`S_(8)` =
`3 * (85)`.

`S_(8)` =
`-255)`.

Therefore,
`S_(8)` =
`-255)`.