x2+y2−8x+7=0x^{2}+y^{2}-8 x+7=0x2+y2−8x+7=0
x2+2y2+4x+12=0x^{2}+2 y^{2}+4 x+12=0x2+2y2+4x+12=0
x2+y2=3x^{2}+y^{2}=3x2+y2=3
x2+y2=42x^{2}+y^{2}=4^{2}x2+y2=42
