$\sum_{n=1}^{\infty} (0.99)^{n-1}$

$\sum_{n=1}^{\infty} (\frac{1}{2})^n$

$\sum_{n=1}^{\infty} (-1.1)^{n-1}$

$\sum_{n=1}^{\infty} (\frac{e}{\pi})^{n-1}$