(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

If (N,R) indicates number of combinations of R objects selected from set of N objects N >=r then prove :

R

E (N,r) x (M,R-r) = (N+M, R)

r=0

E specifies the usual capital sigma notion for a sum.

3. The attempt at a solution

Just dont know how to tackle this? Inductive proof may be possible but we have three variables N, M and R, so its non trivial?

Any clues?

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# Homework Help: How to prove?

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