SOLUTION: Prove nCr = n/(n-r) * n-1Cr using an analytic and combinatoial proof

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Question 431819: Prove nCr = n/(n-r) * n-1Cr using an analytic and combinatoial proof
Answer by richard1234(7193) About Me  (Show Source):
You can put this solution on YOUR website!
The right hand side is equal to

%28n%2F%28n-r%29%29%28%28n-1%21%29%2F%28n-1-r%29%21r%21%29

Since n%28n-1%29%21+=+n%21, and %28n-r%29%28n-1-r%29%21+=+%28n-r%29%21 the right hand side is equal to

n%21%2F%28n-r%29%21r%21, same as the left hand side.