- #1

zoxee

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I always see two formulas for n choose k

the first one:

## \dfrac{n(n-1)(n-2)...(n-k+1)}{k!} ## and the second ## \dfrac{n!}{k!(n-k)!} ## just curious on how you get from one to the other

I multipled the first one by (n-k)! and got ## \dfrac{n(n-1)(n-2)...(n-k+1)(n-k)!}{k!(n-k)!} = \dfrac{n(n-1)(n-2)...(n-k+1)!}{k!(n-k)!} ## but not sure how to proceed... thanks

the first one:

## \dfrac{n(n-1)(n-2)...(n-k+1)}{k!} ## and the second ## \dfrac{n!}{k!(n-k)!} ## just curious on how you get from one to the other

I multipled the first one by (n-k)! and got ## \dfrac{n(n-1)(n-2)...(n-k+1)(n-k)!}{k!(n-k)!} = \dfrac{n(n-1)(n-2)...(n-k+1)!}{k!(n-k)!} ## but not sure how to proceed... thanks

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