用二项式定理证明(n+1)^n-1能被n^2整除

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原式=n^n＋C(n,1)*n^(n-1)＋C(n,2)*n^(n-2)+...＋C(n,2)*n^2＋C(n,1)*n ＝n^n＋C(n,1)*n^(n-1)＋C(n,2)*n^(n-2)+...＋C(n,2)*n^2＋n^2 =n^2 [n^（n-2）＋C(n,1)*n^(n-3)＋C(n,2)*n^(n-4)+...＋C(n,2)＋1]所以(n+1)^n...