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        riddles >> medium >> binomial coefficients
        
(Message started by: Christine on Sep 26th, 2013, 12:43pm)
Title: binomial coefficients
Post by Christine on Sep 26th, 2013, 12:43pm
C(n,k) = n!/(k!(n-k)!)

Is the equality (r-k) * C(r, k) = r * C(r-1, k) always true?
Title: Re: binomial coefficients
Post by pex on Sep 26th, 2013, 12:54pm

on 09/26/13 at 12:43:26, Christine wrote:
C(n,k) = n!/(k!(n-k)!)

Is the equality (r-k) * C(r, k) = r * C(r-1, k) always true?

Yes: use n! = n * (n-1)! a couple of times.


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