4/25x3/8÷4/25×3/8=4/25乘3/8除4/25乘3/8=?

(5^4x3^3-5^3x3^2+5^2x3)÷15=? 用配方法化二次型刘老师您好：f（x1,x2,x3）=x1^2+3x2^2+8x3^2+4x1x2+6x1x3+10x2x3配方后得f（x1,x2,x3）=（x1+2x2+3x3）^2-(x2+x3)^2 做可逆线性变换y1=x1+2x2+3x3 x1=y1-2y2-y3y2=x2+x3 即 x2=y2-y3y3=x3 x3=y3「即」前面的式 解线性方程组x1+x2+3x3+4x4=5 2x1+4x2+4x3+6x4=8 -x1-2x2-x3-2x4=-3 X1+X2-3X3-X4=1 3X1-X2-3X3+4X4=4 X1+5X2-9X3-8X4=0 解线性方程组 求非其次线性方程组 X1+X2-3X3-X4=1 3X1-X2-3X3+4X4=4 X1+X2-9X3-8X4=0 线性代数,x1+x2-3x3-x4=0 3x1-x2-3x3+4x4=0 x1+5x2-9x3-8x4=0 解线性方程组 X1+2X2+3X3=4 3X1+5X2+7X3=9 5X1+8X2+11X3=14 解线性方程组 X1+2X2+3X3=4 3X1+5X2+7X3=9 5X1+8X2+11X3=14 求线性方程组 2 x1+3 x2+x3=4;x1-2 x2+4 x3=-5;3 x1+8 x2-2 x3=13;4 x1-x2+9 x3=-6的全部解 求方程组X1-3X2-2X3-X4=1 3X1-8X2-4X3-X4=0 -2X1+X2-4X3+2X4=1 -X1-2X2-6X3+X4=2的解 求线性方程组{X1-3x2-2x3-X4=1;3X1-8X2-4X3-X4=0;-2X1+X2-4X3+2X4=1;-X1-2X2-6X3+X4=2的一般解. 求线性方程组x1-3x2-2x3-x4=1,3x1-8x2-4x3-x4,-2x1+x2-4x3+2x4=1,-x1-2x2-6x3+x4= 消元法解线性代数2X1+3X2+ X3=4X1-2X2+4X3=-53X1+8X2-2X3=134X1-X2+9X3=-6 消元法解线性代数4X1+2X2-X3=23X1-X2+2X3=1011X1+3X2 =8 求极限(2x3-3x+4)/(8+5x2-3x3) 求下列非齐次线性方程组的解x1+x2-3x3-x4=13x1-x2-3x3+4x4=4x1+5x2-9x3-8x4=0我已经算到x1+x2-3x3-x4=1-4x2+6x3+7x4=1该怎么分别用x1 x2 x3 x4来表示呢? mathematica如何求解含有三角函数的方程?FindRoot[{3 x1^3 + 2 x2 - 5 + Sin[x1 - x2] Sin[x1 + x2] == 0,-x1*Exp[x1 - x2] + x2 (4 + 3 x2^2) + 2 x3 + Sin[x2 - x3] Sin[x2 + x3] - 8 == 0,-x2*Exp[x2 - x3] + 4 x3 - 3 ==0},{x1,Pi/2},{x2,2},{x3,0}] LP模型：max 50x1 +80x2 +30x3 +40x4 +15x5s.t.500x1 +1000x2 +100x3 +300x4 +80x5 ≤20 000x1 + x2 ≥8x3 + x4 ≥15500x1+ 1000x2 ≤12 000x1 ≤16,x2≤10,x3≤24,x4≤4,x5≤25,x1,x2,…,x5 ≥0.max z=50x1 +80x2 +70x3,s.t.12x1 +7x2 +8x3 ≤ 80002x1