## Precalculus (6th Edition) Blitzer

$\frac{4}{3}=1.333$
The sum of an infinite geometric sequence is given as: $S=\dfrac{a_1}{1-r}$ Here, $a_1=2$ and the common ratio is $r=\dfrac{-1}{2}$ $S=\dfrac{a_1}{1-r}$ Now, $S=\dfrac{2}{1-(-\dfrac{1}{2})}=\dfrac{4}{2+1}=1.333$