Question

the sum of the first n terms of a sequence is 20 - 10 / 2 ^ n - 1 find the sum of the first five terms​

Answer 1

`S_5=(170)/(9)`

Explanation:

Given that,

The sum of first n term of a sequence is
`S_n=20-(10)/(2n-1)`

We need to find the sum of the first 5 terms.

Put n = 5,

`S_5=20-(10)/(2(5)-1)\\\\=20-(10)/(10-1)\\\\=20-(10)/(9)\\\\=(170)/(9)`

So, the sum of first 5 terms is equal to
`(170)/(9)`.