3x (1x2+2X3+3x4...+99x100)=

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)=? 1x1-2x2+3x3-4x4+5x5-6x6.-100x100+101x101 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 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 1分解因式：2x4-x3-13x2-15=?2.分解因式：x5+x4+x3+x2+x+1=?3分解因式：x4-4x2+6