SOLUTION: prove that: nCr=(n/r)(n-1)C(r-1)

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Question 21401: prove that: nCr=(n/r)(n-1)C(r-1)
Answer by venugopalramana(3286) About Me  (Show Source):
You can put this solution on YOUR website!
LHS=nCr=n!/[(n-r)!r!]
RHS=(n/r)(n-1)C(r-1)=(n/r)[(n-1)!/{(n-1)-(r-1)}!(r-1)!]
=[n(n-1)!/{(n-1-r+1)!(r-1)!r]=n!/[(n-r)!r!]=LHS