Sum...

Jan 2013
96
0
Let m,n be two natural numbers. Prove that:
\(\displaystyle \displaystyle \sum\limits_{i=-m}^{n} (-1)^i \frac{(2m+i)! (2n-i)!}{((m+i)!)^2((n-i)!)^2}=1\)
 
Feb 2011
68
0
yo79 could you please tell us where did you find this?