x+y+z=2,xy+xz+yz=a,xy+z=a,求a的取值范围

(2X+Z-Y)/(X^2-XY+XZ-YZ)-(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 x+y+z=2,xy+xz+yz=a,xy+z=a,求a的取值范围 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 已知X+Y+Z=a,XY+YZ+XZ=b,求X*X+Y*Y+Z*Z的值 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) 若实数xyz满足(x-2y+z)^2+4(x-y)(y-z)=0 A xy-yz=0 B xy+yz=0 C xy-xz=0 D xy+xz=0 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 求(2X+Z-Y)/(X^2-XY+XZ-YZ)-(2X+Y+Z)/(X^2+XY+XZ+YZ) 方程组：(x+y)/xy=3 (y+z)/yz=4 (z+x)/xz=5 若xyz+xy+yz+xz+x+y+z=2008,则x+y+z=多少, 证明 当x+y+z=1时,x/yz+y/xz+z/xy≥9 xy/x+y=1,xz/x+z=2,yz/y+z=3,求x的值 如果1=xy/x+y,2=yz/y+z,3=xz/x+z,则x的值? 已知1=xy/x+y,2=yz/y+z,3=xz/x+z,求 X的值