(2xy^2-3x^3y)(-2xy^2+3x^2y) 2.(2x-3y+4z)(2x+3y-4z)

已知3x－y+2z=x+2y+3z=0,求（3x^－xy+2y^)/(2x^+4xy+y^)值? 5yz/(y+z)=6,4xy/(z+x)=3,3xy/x+y=2 已知三个数x,y,z,满足xy/x+y=-2，yz/y+z=4/3,zx/z+x=-4/3,求(xyz)/(xy+yz+ 实数x、y、z满足x=6-3yx+3y-2xy+2z 已知实数x,y,z满足x²-6xy+10y²+4y+|z²-3z+2|+4=0,求(x+y 已知x>0,y>0,z>0,证明x^3/(x+y)+y^3/(y+z)+z^3/(z+x)≥(xy+xz+yz)/2 三元二次方程组(XY+X)/(X+Y+1)=2(XZ+2X)/(X+Z+2)=3(Y+1)(Z+2)/(Z+Y+3)=4 xy／x+y＝1,yz／y＋z＝2,xz／x＋z＝3求x,y 证明 (x+y+z)^2>3(xy+yz+zx) 1.已知：X+Y+Z=3Y=2Z,求X/X+Y+Z的值 2.已知：1/X-1/Y=3,求2X+3XY-2Y/X-2XY- 已知x^3+y^3-z^3=96,xyz=4,x^2+y^2+z^2-xy+xz+yz=12,则x+y-z等于 (x-3y+z)^2+/ 5x-4y+z/=0 且xyz≠0 xy+yz+zx/x^2+y^2+z^2