Binomial Theorem/Abel's Generalisation

Theorem

 * $\ds \paren {x + y}^n = \sum_k \binom n k x \paren {x - k z}^{k - 1} \paren {y + k z}^{n - k}$

for $n \in \Z_{\ge 0}$ and $x \in \R_{\ne 0}$.