Binomial Theorem/Extended

Theorem
Let $r, \alpha \in \C$ be complex numbers.

Let $z \in \C$ be a complex number such that $\left|{z}\right| < 1$.

Then:
 * $\displaystyle \paren {1 + z}^r = \sum_{k \mathop \in \Z} \dbinom r {\alpha + k} z^{\alpha + k}$

where $\dbinom r {\alpha + k}$ denotes a binomial coefficient.