A useful Geometric Series formula
$ \sum_{n = M}^N \alpha^n = \frac{\alpha^M - \alpha^{N-1}}{(1 - \alpha)} $
- What if $ \alpha=1 $????
- For what values of M and N does this formula hold? Can they both be negative? Does N need to be greater than M?
$ \sum_{n = M}^N \alpha^n = \frac{\alpha^M - \alpha^{N-1}}{(1 - \alpha)} $