Sum...

For discussing Olympiad Level Algebra (and Inequality) problems
yo79
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Joined:Mon Feb 04, 2013 1:01 am
Sum...

Unread post by yo79 » Sat Apr 27, 2013 4:05 pm

Let m,n be two natural numbers. Prove that:
$\displaystyle \sum\limits_{i=-m}^{n} (-1)^i \frac{(2m+i)! (2n-i)!}{((m+i)!)^2((n-i)!)^2}=1$

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