作业帮1X2+2x3+3x4+...99x100 =
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1X2+2x3+3x4+...99x100 =
1X2+2x3+3x4+...99x100 =
1X2+2x3+3x4+...99x100 =
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
1/1x2+1/2x3+1/3x4+1/4x5.1/9x10简算
计算：1/1x2+1/2x3+1/3X4+...+1/9x10=?
1X2/1+2X3/1+3X4/1+……+9X10/1=_____
计算：1/1x2+1/2x3+1/3X4+...+1/9x10=?
-1/1x2-1/2x3-1/3x4-.-1/9x10
1x2/1+2x3/1+3x4/1+……+9x10/1
1/(1x2)+1/(2x3)+1/(3x4)+.+1/(9x10)
1X2/1—2X3/1—3X4/1—...—9X10/1=?
1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11
1x2+2x3+3x4+.99x100=?
1X2+2x3+3x4+...99x100 =
已知:x1=1/2+1/3,x2=1/3+1/4,x3=x2+x1,x4=x3+x2.,x10=x9+x8,求：x7/x1+x2+...+x10
1/1x2+1/2x3+1/3x4+……+1/9x1o= 1/1x2-1/2x3-1/3x4……-1/1x2+1/2x3+1/3x4+……+1/9x1o=1/1x2-1/2x3-1/3x4……-1/9x10=
用克拉默法则解下列方程组 x1-2x2+3x3-4x4=4 x2-x3+x4=-3 x1+3x2+2x4=1 -7x2+3x3+x4=3x1-2x2+3x3-4x4=4x2-x3+x4=-3 x1+3x2+2x4=1 -7x2+3x3+x4=3
解方程组X1-2x2+3x3-x4=1,3x1-x2+5x3-3x4=2,2x1+x2+2x3-2x4=3
写出方程组2*x1+x2-x3+x4=1,x1+2*x2+x3-x4=2,x1+x2+2*x3+x4=3的通解?
求非齐次线方程组的通解 ：2x1+x2-x3+x4=1 x1+2x2+x3-x4=2 x1+x2+2x3+x4=3
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