Z=X^2+3XY+3Y^2-6X-3Y-6的极值是多少

已知4x-3y=6z 2x+4y=14z 求2xy/x^+y^ 已知4x-3y=6z 2x+4y=14z 求2xy/x^+y^ 若|x-3|+|y+2|+|2z+1|=0,求(xy-yz)(y-x+z) 24xy^2z^2(x+y+z)-32xyz(z-x-y)^2+8xyz^3(z-x-y) 24xy^2z^2(x+y+z)-32xyz(z-x-y)^2+8xyz^3(z-x-y) 已知3x－y+2z=x+2y+3z=0,求（3x^－xy+2y^)/(2x^+4xy+y^)值? (x+y-xy)/(x+y+2xy)=(y+z-2yz)/(y+z+3yz)=(z+x-3zx)/(z+x+4zx),且2/x=3/y=1/z,则xyz=? 已知（x+y-xy）/(x+y+2xy)=(y+z-2yz)/(y+z+3yz)=(z+x-3zx)/(z+x+4zx),且2/x=3/y-1/z,则xyz=? z=x^2-xy+y^3 求全微分dz 分式题:xy=x+y,yz=2(y+z),zx=3(z+x),求xyz/(xy+yz+xz)xy=x+y,yz=2(y+z),zx=3(z+x),求xyz/(xy+yz+xz) 已知XY+X/X+Y+1=2 XZ+2X/X+Z+2=3 (Y+1)(Z+2)/Y+Z+3=4 求X+Y+Z的值已知(XY+X)/(X+Y+1)=2 (XZ+2X)/(X+Z+2)=3 [(Y+1)(Z+2)]/(Y+Z+3)=4 求X+Y+Z的值 若x+y=4,x^3+y^3=(x+y)(x^2-xy+y^2)z,求x^3+12xy+y^3的值. x²-y²+5x+3y+4（x+y-2xy)(x+y-z)+(xy-1）² 已知xy/x+y=2/3,yz/y+z=6/5.xz/x+z=3/4求x-z^y 已知实数x,y,z满足x+3y=6,2xy-z^2=6,求x、y、z的值 已知实数x .y.z.满足2^x=3^y=6^z 求证:xy+yz=xz 若：X^2-4X+Y+6Y+√ Z-3+13=0求（xy)^z的值 求证：(x^3/x+y)+(y^3/y+z)+(z^3/z+x)大于等于（xy+yz+zx)/2