nasmith99 29.01.2016 21:26 Just expand and solve: (x−y+z)2=x2−y2+z2 x2+y2+z2−2xy−2yz+2zx=x2−y2+z2 y2−xy−yz+zx=0 (y−x)(y−z)=0 So either y=x or y=z.