permutation

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February 1st 2013, 05:38 PM
miki

permutation

why is nPk "n!/(n-k)!" ?
i'm understanding that nPk = n*(n - 1)***(n - k + 1).
uhh...
February 1st 2013, 05:59 PM
Plato

Re: permutation

Quote:

Originally Posted by miki

why is nPk "n!/(n-k)!" ?
i'm understanding that nPk = n*(n - 1)***(n - k + 1).
uhh...

$N!=N\cdot(n-1)\cdots(N-k+1)(N-k)!$

Example $_{10}P_4=10\cdot 9\cdot 8\cdot 7=\frac{10!}{(10-4)!}$
February 1st 2013, 06:46 PM
miki

Re: permutation

thanks a lot !
i understod your reply meaning.
i try it!

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