x2+y2+8x+6y+21=0x^{2}+y^{2}+8 x+6 y+21=0x2+y2+8x+6y+21=0
x2+y2−8x−6y+21=0x^{2}+y^{2}-8 x-6 y+21=0x2+y2−8x−6y+21=0
x2+y2−8x+6y+25=0x^{2}+y^{2}-8 x+6 y+25=0x2+y2−8x+6y+25=0
x2+y2+8x−6y+25=0x^{2}+y^{2}+8 x-6 y+25=0x2+y2+8x−6y+25=0