Finite Geometric Series: $ \sum_{k=0}^n x^k = \left\{ \begin{array}{ll} \frac{1-x^{n+1}}{1-x}& \text{if } x\neq 1\\ n+1 & \text{else}\end{array}\right. $
Finite Geometric Series: $ \sum_{k=0}^n x^k = \left\{ \begin{array}{ll} \frac{1-x^{n+1}}{1-x}& \text{if } x\neq 1\\ n+1 & \text{else}\end{array}\right. $