1X2+2x3+3x4+...99x100 =

来源：学生作业帮编辑：神马作文网作业帮分类：数学作业时间：2024/11/14 10:37:41

n(n+1)
=(1/3) { n(n+1)(n+2) - (n-1)n(n+1) }
1x2+2x3+3x4+...99x100
= 1x2 + (1/3) { (2x3x4 - 1x2x3) + (3x4x5 - 2x3x4) +...+(99x100x101 - 98x99x100) }
= 1x2 + (1/3) { 99x100x101 -1x2x3 }
= (1/3) 99x100x101
=333300

1分之1x2+1分之2x3+1分之3x4.+1分之99x100 计算1x2+2x3+3x4+4x5+...+99x100 一定要帮我啊!(1/1x2)+(1/2x3)+(1/3x4)+(1/4x5)+.+(1/99x100)=? 1/1x2+1/2x3+1/3x4+1/4x5+.+1/98x99+1/99x100 1/1X2+1/2x3+1/3x4+1/4x5+.+1/98x99+1/99x100求结果! 2/1x2+2/2x3+2/3x4+2/4x5+...+2/98x99+2/99x100 求1x2,2x3,3x4,4x5,……98x99,99x100的倒数和 1x1-2x2+3x3-4x4+5x5-6x6.-100x100+101x101 1/(1x2)+1/(2x3)+1/(3x4)+．．．．．．+1/(99x100)=?要计算过程．简便计算1/2+1/2x3+1/3x4+1/4x5+...+1/99x100 1X2+2X4+3X6+.50X100 求线性方程组 x2-x3-x4=0 x1+x2-x3+3x4=1 x1-x2+x3+5x4=-1 x1+2x2-2x3+