Answer
$\dfrac{2}{3}$
Work Step by Step
Formula to find Nth partial sum of a geometric series is:
$s_n=\dfrac{a(1-r^n)}{1-r}$
Here, $r=\dfrac{-1}{2}, a=1$
Thus, $s_n=[\dfrac{1(1-(\dfrac{-1}{2})^n)}{1-(\dfrac{-1}{2})}]$
Formula to find Sum of a geometric series can be found as:
$S=\dfrac{a}{1-r}=\dfrac{1}{(\dfrac{3}{2})}=\dfrac{2}{3}$
