Answer
$\dfrac{2}{3}$
Work Step by Step
The general formula to find the sum of an infinite Geometric series is given as:
$ S_{n}=\dfrac{a_1}{(1-r)}$
and $ r=\dfrac{a_2}{a_1}=\dfrac{-1/2}{1}=\dfrac{-1}{2}$
Now, $ S_{n}=\dfrac{a_1}{(1-r)}=\dfrac{1}{1-(-\dfrac{1}{2})}$
Our answer is: $ S_{n}=\dfrac{1}{3/2}=\dfrac{2}{3}$
