问题描述: 1X2X3+2X3X4+.+n(n+1)(n+2) 1个回答 分类:综合 2014-10-02 问题解答: 我来补答 1*2*3+2*3*4+.+n*(n+1)(n+2)=1/4[(1*2*3*4-0*1*2*3)+(2*3*4*5-1*2*3*4)+.+n(n+1)(n+2)(n+3)-(n-1)n(n+1)(n+2)]=1/4*n(n+1)(n+2)(n+3) 展开全文阅读