I have a bunch of equations that I must prove 'using combinatorics', which means double counting or some sort of bijective mapping. I haven't done this before, and I'd like to know, as an example, how the following can be proved 'combinatorially':(adsbygoogle = window.adsbygoogle || []).push({});

[tex]\left(\begin{array}{cc}{n+1}\\{m+1}\end{array}\right)=\sum_{i=0}^{n-m}\left(\begin{array}{cc}{m+i}\\m\end{array}\right)[/tex]

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# Homework Help: Combinatorial Proof

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