x^2+y^2+z^2>=yz+xz+xy证明

(2X+Z-Y)/(X^2-XY+XZ-YZ)-(Y-Z)/(X^2-XY-XZ+YZ) 化简(2x-y-z/x^2-xy-xz+yz)+(2y-x-z/y^2-xy-yz+xz)+(2x-x-y/z^2-xz-yz+xy) 求(2X+Z-Y)/(X^2-XY+XZ-YZ)-(2X+Y+Z)/(X^2+XY+XZ+YZ) 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) 求证不等式 xyz[yz(y+z)+zx(z+x)+xy(x+y)]>=2(xy+yz+xz)^2 设x,y,z∈R+,xy+yz+xz=1,证明不等式:(xy)^2/z+(xz)^2/y+(yz)^2/x+6xyz≥x+y+zRt f(x,y,z)=yz+xz使得,y^2+z^2=1,yz=3,求f最大值 x+y+z=0 求证：(x^2-y^2)+(xz-yz)=0 若x+y=-z,则(x^2-y^2)+(xz-yz)的值是___ 若x+y=-z,则(x^2-y^2)+(xz-yz)的值为? x+y=-z,则(x^2-y^2)+(xz-yz)的值为 x^2+y^2+xy=25/4,x^2+z^2+xz=169/4,y^2+z^2+yz=36,求xy+xz+yz 已知xy(x+y)^-1=1,yz(y+z)^-1=2,xz(z+x)^-1=3,试求xyz(xy+yz+xz)^-1的值 已知xy(x+y)^-1=1,yz(y+z)^-1=2,xz(z+x)^-1=3,试求xyz(xy+yz+xz)^-1的值 解方程组:1、（x+2y-z）^2+(z-x)^2=0 2、xz^2+yz-5根号下(xz^2+yz+9)+3=0 设f(x,y,z)=x.arcsiny+yz^2+zx^2,求f(xz),f(yz),f(zz) 2yz/x+2xz/y+2xy/z≥2x+2y+2z xy/x+y=1,xz/x+z=2,yz/y+z=3,求x的值