巧算:1x2+2x3+3x4+4x5+5x6+6x7...+8x9

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巧算:1x2+2x3+3x4+4x5+5x6+6x7...+8x9巧算:1x2+2x3+3x4+4x5+5x6+6x7...+8x9巧算:1x2+2x3+3x4+4x5+5x6+6x7...+8x91

巧算:1x2+2x3+3x4+4x5+5x6+6x7...+8x9
巧算:1x2+2x3+3x4+4x5+5x6+6x7...+8x9

巧算:1x2+2x3+3x4+4x5+5x6+6x7...+8x9
1×2+2×3+...+8×9 太长了,就不抄全了.
=1×(1+1)+2×(2+1)+...+8×(8+1)
=1²+2²+...+8²+1+2+...+8
=8×9×17/6 +8×9/2
=204+36
=240
利用公式:
1+2+...+n=n(n+1)/2
1²+2²+...+n²=n(n+1)(2n+1)/6

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 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 巧算:1x2+2x3+3x4+4x5+5x6+6x7...+8x9 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+.+15x16 解方程组:x1+x2+x3+x4+x5=7 3x1+2x2+x3+x4-3x5=-2 x2+2x3+2x4+6x5=23 5x1+4x2-3x3+3x4-x5=10 求非其次线性方程组 {x1+2x2+x3+x4+x5=1x1+2x2+x3+x4+x5=12x1+4x2+3x3+x4+x5=2-x1-2x2+x3+3x4-x5=5 2x3+4x4-2x5=6 的一般解 求线性方程组的全部解,并用对应导出组的基础解系表示X1+3X2+5X3-4X4=1 X1+3X2+2X3-2X4+X5=-1 X1-2X2+X3-X4-X5=3 X1-4X2+X3+X4-X5=3 X1+2X2+X3-X4+X5=-1 求解线性方程组 x1-2x2+3x3-x4-x5=2 x1+x2-x3+x4-2x5=1 2x1-求解线性方程组x1-2x2+3x3-x4-x5=2x1+x2-x3+x4-2x5=12x1-x2+x3-2x5=22x1+2x2-5x3+2x4-x5=5 求下列非齐次线性方程组的通解(1){x1+x2+x3+x4+x5=2;x1+2x2-4x5=-2;x1+2x3+2x4+6x5=6;4x1+5x2+3x3+3x4-x5=4}(2){x1-x2+5x3-x4=1;x1+x2-2x3+3x4=1;2x1+3x3+2x4=2;2x1+4x2-11x3+10x4=2}(3){x1+x2+x3+x4+x5=1;3x1+2x2+x3+x4-3x5=0 1x2+2x3+3x4+4x5+5x6---+99x100=? 1x2+2x3+3x4+4x5+5x6+.+99x100 1x1 2x2 3x3 4x4 5x5```````nxn有什么规律 1x1 2x2 格式正确 3x3 4x4 5x5 确定a的值,使线性方程组{X1+X2+X3+X4=1,3X1+2X2+X5+X4=0,X2+2X3+2X4=a,5X1+4X2+3X2+3X4=2 并求通解 matlab线性方程组计算X1+X2-5X3-X4+X5=98X1+5X2-X3+4X5=23X1-7X2-5X3-X4+X5=42X1+X2+8X3+3X4-X5=-86X2+2X3+7X4-2X5=15