1X2+2x3+3x4+……+2013x2014

求线性方程组 x2-x3-x4=0 x1+x2-x3+3x4=1 x1-x2+x3+5x4=-1 x1+2x2-2x3+ 已知无穷数列1x2,2x3,3x4…,n（n+1）,… 求： 1x2+2x3+3x4+4x5+……+10x11 1x2/1+2x3/1+3x4/1+4x5/1+…+39x40/1 求使1x2+2x3+3x4+…+n(n+1) 一道简便计算数学题1X2+2X3+3X4+4X5...+n(n+1)一1X2+2X3+3X4+4X5...+2013X2 求齐次线性方程组x1+2x2+x3+x4+x5=1 2x1+4x2+3x3+x4+x5=2 -x1-2x2+x3+3x4 设线性方程组（x1+2x2-2x3+2x4=2,x2-x3-x4=1 x1+x2-x3+3x4=a） 具体写出方程组：2x1+x2-x3+x4=1;x1+2x2+x3-x4=2;x1+x2+2x3+x4=3的通解 解方程组X2+X3+X4=1 X1+X2+X3=5 X3+X4+X5=-5 X4+X5+X1=-3 X5+X1+X2=2 探究并计算：1/2x4＋1/4x6＋1/6x8＋…＋1/2012x2014 1x1!+2x2!+3x3!+4x4!.nxn!