x2+y2+x−y=0x^{2}+y^{2}+x-y=0x2+y2+x−y=0
x2+y2−x−y=0x^{2}+y^{2}-x-y=0x2+y2−x−y=0
x2+y2−x+y=0x^{2}+y^{2}-x+y=0x2+y2−x+y=0
x2+y2+x+y=0x^{2}+y^{2}+x+y=0x2+y2+x+y=0