计算:1/1x2+1/2x3+1/3x4+.+1/(n-1)n

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计算:1/1x2+1/2x3+1/3x4+.+1/(n-1)n
计算:1/1x2+1/2x3+1/3x4+.+1/(n-1)n

计算:1/1x2+1/2x3+1/3x4+.+1/(n-1)n
1/1x2+1/2x3+1/3x4+.+1/(n-1)n
观察一下
1/1x2=1-1/2
1/2x3=1/2 -1/3
1/3x4=1/3 -1/4
.
.
1/(n-1)n=1/(n-1) - 1/n
然后所有式子相加
1/1x2+1/2x3+1/3x4+.+1/(n-1)n
=1-1/2 +1/2-1/3+1/3-1/4+.-1/(n-1)+1/(n-1)-1/n
=1-1/n
=(n-1)/n

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 因式分解：x4+x3+2x2 +x+1 解方程组X1-2x2+3x3-x4=1,3x1-x2+5x3-3x4=2,2x1+x2+2x3-2x4=3 x1+5x2-x3-x4=-1x1-2x2+x3+3x4=33x1+8x2-x3+x4=1 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的通解解一道方程组x1+x2+x3=5,x2+x3+x4=1,x3+x4+x5=-5,x4+x5+x1=-3,x5+x1+x2=2 100x100-99x99+98x98-97x97+.+4x4-x4-3x3+2x2-1计算计算:1/1x2+1/2x3+1/3x4+.+1/(n-1)n 计算：1/1x2+1/2x3+1/3X4+...+1/9x10=? 计算:1/1x2+1/2X3+1/3x4+...+1/2009x2010 计算 1/1x2+1/2x3+1/3x4+.+1/2009x2010 计算：1/1x2+1/2x3+1/3x4+.+1/2010X2011 计算：1/1x2+1/2x3+1/3X4+...+1/9x10=? 1/1x2+1/2x3+1/3x4+...+1/49x50怎么计算计算1x2+2x3+3x4+4x5+...+99x100 计算1x2+2x3+3x4+……+99x100=?