Abel's binomial theorem states the following
∑ y = 0 m ( m y ) ( w − m ) m − y − 1 ( z + y ) y = w − 1 ( z + w + m ) m {\displaystyle \sum _{y=0}^{m}{\binom {m}{y}}(w-m)^{m-y-1}(z+y)^{y}=w^{-1}(z+w+m)^{m}}
Binomial identity
Weisstein, Eric W. "Abel's binomial theorem". MathWorld.
