x/(xy+x+1)+y/(yz+y+1)+z/(zx+z+1)=x/(xy+x+xyz)+y/(yz+y+1)+z/(zx+z+1)=1/(yz+y+1)+y/(yz+y+1)+z/(zx+z+1)=(1+y)/(yz+y+1)+z/(zx+z+1)=(xyz+y)/(yz+y+xyz)+z/(zx+z+1)=(xz+1)/(zx+z+1)+z/(zx+z+1)=(zx+z+1)/(zx+z+1)=1
