求证n(n+1)(n+2)能被6整除

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求证n(n+1)(n+2)能被6整除

求证n(n+1)(n+2)能被6整除
求证n(n+1)(n+2)能被6整除

求证n(n+1)(n+2)能被6整除
当n=1时
n(n+1)(n+2)=6
能被6整除
设n=k时,
n(n+1)(n+2)能被6整除
即,k(k+1)(k+2)能被6整除
当n=k+1时,
(k+1)(k+2)(k+3)-k(k+1)(k+2)
=(k+1)(k+2)·[(k+3)-k]
=3(k+1)(k+2)
因为,k+1、k+2必定一奇一偶,
所以,(k+1)(k+2)是2的倍数
所以3(k+1)(k+2)是6的倍数
从而,(k+1)(k+2)(k+3)是6的倍数.
所以结论当n=k+1时也成立.
于是,
n(n+1)(n+2)能被6整除