求证 (14 19:41:33)求证:Ank+kAnk-1=An+1k

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求证 (14 19:41:33)求证:Ank+kAnk-1=An+1k

求证 (14 19:41:33)求证:Ank+kAnk-1=An+1k
求证 (14 19:41:33)
求证:Ank+kAnk-1=An+1k

求证 (14 19:41:33)求证:Ank+kAnk-1=An+1k
展开:
Ank= (n-0)(n-1)(n-2)*…*(n-k+2)(n-k+1)
kAnk-1= k(n-0)(n-1)(n-2)*…*(n-k+2)
提取(n-0)(n-1)(n-2)*…*(n-k+2)
Ank+kAnk-1=(n-0)(n-1)(n-2)*…*(n-k+2)*(n-k+1+k)
=(n+1)(n-0)(n-1)(n-2)*…*(n-k+2)
=An+1k