Answer
$15-3+\frac{3}{5}-...-\frac{3}{625}=\displaystyle \sum_{n=1}^{6}15(-\frac{1}{5})^{n-1}$
Work Step by Step
$-\frac{3}{625}=-\frac{3}{625}\frac{15}{15}=15(-\frac{1}{3125})=15(-\frac{1}{5})^5$
$15-3+\frac{3}{5}-...-\frac{3}{625}=15(-\frac{1}{5})^0+15(-\frac{1}{5})^1+15(-\frac{1}{5})^2+...+15(-\frac{1}{5})^5=\displaystyle \sum_{n=1}^{6}15(-\frac{1}{5})^{n-1}$
