1x2+2x3+3x4+4x5+5x6+6x7+7x8+.+nx（n+1） 要公式,别搞太深奥!

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1x2+2x3+3x4+4x5+5x6+6x7+7x8+.+nx（n+1） 要公式,别搞太深奥!
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1x2+2x3+3x4+4x5+5x6+6x7+7x8+.+nx（n+1） 要公式,别搞太深奥!
1x2+2x3+3x4+4x5+5x6+6x7+7x8+.+nx（n+1） 要公式,别搞太深奥!

1x2+2x3+3x4+4x5+5x6+6x7+7x8+.+nx（n+1） 要公式,别搞太深奥!
1x2+2x3+3x4+…+n(n+1)
=1x(1+1)+2x(2+1)+3x(3+1)+…n(n+1)
=(1^2+2^2+3^2+…+n^2)+(1+2+3+…+n)
=n(n+1)(2n+1)/6+n(n+1)/2
=n(n+1)[(2n+1)+3]/6

x1-x2+x3=1x2-x3+x4=21若x1,x2,x3,x4,x5满足方程组 x3-x4+x5=3x4-x5+x1=4x5-x1+x2=5求x2 x3 x4的值2已知 x1+x4+x6+x7=39 x2+x4+x5+x7=49 x3+x5+x6+x7=41 x4+x7=13 x5+x7=14 x6+x7=9 x1+x2+x3+x4+x5+x6+x7=9求x7的值若x1,x2,x3,x4,x5满足方程组 x1-x 1x2+2x3+3x4+4x5+5x6---+99x100=? 1x2+2x3+3x4+4x5+5x6+.+99x100 巧算：1x2+2x3+3x4+4x5+5x6+6x7...+8x9 1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+......1/2008x2009 1/1x2+2/1x3+3/1x4+4/1x5+5/1x6+6/1x7= 1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11 (2X2)/1X3+(4X4)/(3X5)+(6X6)/(5X7)+...+(20X20)/(19X21)==? 1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9= 1x1-2x2+3x3-4x4+5x5-6x6.-100x100+101x101简便算法答案 2013/1x2+2013/2X3+2013/3X4+2013/4X5+2013/5X6简便计算, 帮我用lingo或者lindo算个题呗?x1+x4+x5+x6+x7>20x1+x2+x5+x6+x7>13x1+x2+x3+x6+x7>10x1+x2+x3+x4+x7>12x1+x2+x3+x4+x5+>16x2+x3+x4+x5+x6+>18x3+x4+x5+x6+x7>20格式不对也改下哈,>在lingo中应该和>=一样吧?min=(5x1+4x2+3x3+3x4+3x5+3x6+4x7) x1-x2+x3=1 x2-x3+x4=2 x3-x4+x5=3 x4-x5+x1=4 x5-x1+x2=5 求x1,x2,x3,x4,x5 求非齐次线性方程组的通解x1+3x2+5x3-4x4=1x1+3x2+2x3-2x4+x5=-1x1-2x2+x3-x4-x5=3x1+2x2+x3-x4-x5=3 求编程高手.求x1+2*x2+3*x3+4*x4+5*x5+9*x6的最小值其中x1+x2+x3 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 若x1,x2,x3,x4,x5满足方程组：x1-x2+x3=1 x2-x3+x4=2 x3-x4+x5=3 x4-x5+x1=4 x5-x1+x2=5 求x2,x3,x4的少打了个字，是求x2，x3，x4的值 计算：1/1x2+1/2x3+1/3x4+1/4x5+1/5x6+1/6x7+1/7x8+1/8x9+1/9x10.