# How do you find the sum of the infinite geometric series 1/2 - 1/6 + 1/18 - ...?

The common ratio is $r = - \frac{1}{3}$ and the infinite sum equals to
$S = {a}_{1} \cdot \left(\frac{1}{1 - r}\right)$ where ${a}_{1} = \frac{1}{2}$ hence
$S = \frac{3}{8}$