Let C(n,k) denote n choose k.
Please show that
n
sigma (-1)^k*C(n,k)*(n-k)^n=n!
k=0
This identity can be obtained by double counting method, but I hope
to see any other proof.
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※ 編輯: gg 來自: 114.45.218.166 (11/22 21:48)