1x2X3+2x3X4+3x4X5+…+7X8X9=?

来源：学生作业帮编辑：搜搜考试网作业帮分类：数学作业时间：2024/05/17 05:07:43

一般的,有：
(n-1)n(n+1)
=n^3-n
{n^3}求和公式：Sn=[n(n+1)/2]^2
{n}求和公式：Sn=n(n+1)/2
1x2x3+2x3x4+3x4x5+.+7x8x9
=2^3-2+3^3-3+...+8^3-8
=(2^3+3^3+...+8^3)-(2+3+...+8)
=[(8*9/2)^2-1]-8*9/2+1
=1260

1x2X3+2x3X4+3x4X5+…+7X8X9=? 1x2x3+2x3x4+3x4x5+...+7x8x9=, 1x2x3+2x3x4+3x4x5+…+8x9x10 1/1x2x3+1/2x3x4+1/3x4x5 1x2x3+2x3x4+3x4x5+.+10x11x12 数学简便计算1/1x2x3+1/2x3x4+1/3x4x5……+1/20x21x22=? 1x2x3+2x3x4+3x4x5……+10x11x12巧算请在两天之内回答 1/1x2x3+1/2x3x4+1/3x4x5+1/4x5x6+.+1/48x49x50= 1/1x2x3+1/2x3x4+1/3x4x5+.+1/11x12x13= 1/1x2x3+1/2x3x4+1/3x4x5+.+1/9x10x11= 请1/1x2x3+1/2x3x4+1/3x4x5+1/4x5x6= 1/(1x2x3)+1/(2x3x4)+1/(3x4x5)+.1/(20x21x22)=?