Abel's binomial theorem explained

Abel's binomial theorem, named after Niels Henrik Abel, is a mathematical identity involving sums of binomial coefficients. It states the following:

m
\sum
k=0

\binom{m}{k}(w+m-k)m-k-1(z+k)k=w-1(z+w+m)m.

Example

The case m = 2

\begin{align} &{}\binom{2}{0}(w+2)1(z+0)0+\binom{2}{1}(w+1)0(z+1)1+\binom{2}{2}(w+0)-1(z+2)2\\ &=(w+2)+2(z+1)+

(z+2)2
w

\\ &=

(z+w+2)2
w

. \end{align}

See also