问题 填空题

当n为任意实数,k为某一特定整数时,等式n(n+1)(n+2)(n+3)+l=(n2+kn+1)2成立.则k=______.

答案

n(n+1)(n+2)(n+3)+l,

=(n2+3n)(n2+3n+2)+l,

=(n2+3n)2+2(n2+3n)+l,

=(n2+3n+1)2

∵(n2+kn+1)2=(n2+3n+1)2

∴k=3,

故答案为:3.

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