Simplifincation of an equation involving Binomial Cofficients

Revision en1, by MazzForces, 2017-12-12 11:53:43

Hi, good day to U'll.

I have the following equation :

 = 

Can you help me with a proof for this ? BTW, this relates to the last part of the following problem : Link. The editorial for the problem tells us to convert the lhs to the rhs w/o any proof or explanation on how it is obtained. Any help would be useful

Thank You

Tags combinatorics, binomial coefficients

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en1 English MazzForces 2017-12-12 11:53:43 621 Initial revision (published)