x-y=1y-z=-2x-z=-1x²+y²+z²-xy-yz-zx=1/2[(x²-2xy+y²)+(x²-2xz+z²)+(y²-2yz+z²)]=1/2[(x-y)²+(y-z)²+(z-x)²]=1/1(1²+2²+1²)=3如追加其...