Expand the summation: $\sum_{i=1}^{k+1}i(i!)$

My solution is:


But I think it is wrong. Please help. Thanks


Write $i(i!)$ as $(i+1-1)i!=(i+1)!-i!$ before summing.

  • 1
    $\begingroup$ thank you. you are amazing. $\endgroup$ – gordon sung Jun 21 '15 at 7:54

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