# Math Help - nth partial sum

1. ## nth partial sum

Find the series whose nth partial sum is:

sn = (-1 + 2^n) / 2^n

And find the sum s of the series

2. Originally Posted by jzellt
Find the series whose nth partial sum is:

sn = (-1 + 2^n) / 2^n
$T_{n}=S_{n}-S_{n-1}=...$, simplify then you got the nth term.

Originally Posted by jzellt
And find the sum s of the series
$s=\lim_{n\rightarrow\infty}S_{n}=\lim_{n\rightarro w\infty}\frac{-1+2^{n}}{2^{n}}=\lim_{n\rightarrow\infty}\frac{-\frac{1}{2^{n}}+1}{1}=...$