z=2xy/（x^2+y^2) x.y属于（1,3）内,用matlab画出图像.

代数 x^-y^/ x^-(y-z)^ 除以 x^+2xy+y^/(x-y)^-z^ 乘 x^+xy-xz/x^-xy 化简(y-x)(z-x)/(x-2y+z)(x+y-2z)+（z-y)(x-y)/(xy-2z)(y+z-2x)+(x-z)(y-z)/(y+z-2x)(x-2y+z)速速回答 设z=f(x^2-y^2,e^（xy)),求偏导z/x,偏导z/y (x^2-y^2)/[x^2-(y-z)^2]/[x^2+2xy+y^2]/[(x-y)^2-z^2]*[x^2+xy-xz]/[x^2-xy]= 若x+y=6,xy=-8,求代数式(x+y-z)^2+(x+y-z)(x+y+z)-2·z(x-y) 2分之一(x+y+z)的平方＋2分之一（x-y-z)(x-y+z)-z(x+y),其中x-y=6,xy=21 若x-y=6,xy=-8,求代数式(x+y+z)²+(x-y-z)(x-y+z)-2·z(x+y)的值 化简x^2-yz/[x^2-(y+z)x+yz]+y^2-zx/[y^2-(z+x)y+zx]+z^2-xy/[z^2-(x+y)z+xy] 已知XY=2(X+Y),YZ=4(Y+Z),ZX=5(Z+X),求X,Y,Z已知XY=2(X+Y),YZ=4(Y+Z),ZX=5(Z+X),求X,Y,Z 方程组xy/x+y=2 yz/y+z=4 zx/x+z=5 求x,y,z 已知实数x,y,z,满足那么x+y=6,z^2=xy-9,求(x+y)^z (xy-1)^2+(x+y-z)(x+y-zxy)因式分解 (2X+Z-Y)/(X^2-XY+XZ-YZ)-(Y-Z)/(X^2-XY-XZ+YZ) 已知x,y,z∈R,求证:x^2+y^2>=xy+x+y-1 x^2(y+z)^2-2xy(x-z)(y+z)+y^2(x-z)^2 =[x(y+z)-y(x-z)]^2 =(xz+yz)^2 =z^2(x+y)^2 x^2+y^2-2x+4y最小值为z,则（xy）^z= 若|x-3|+|y+2|+|2z+1|=0,求(xy-yz)(y-x+z) z=ln(xy+x/y),则δ^2z/δxδy=什么