X2+Y2-2X-5=0
x^2-2x+1+y^2=6
(x-1)^2+y^2=6
圆心坐标(1,0)和半径长√6
X2+Y2+2X-4Y-4=0
x^2+2x+1+y^2-4y+4=9
(x+1)^2+(y+2)^2=9
圆心坐标(-1,-2)和半径长3
/a/,/b/为绝对值
X2+Y2+2aX=0
x^2+2ax+a^2+y^2=a^2
(x+a)^2+y^2=a^2
圆心坐标(-a,-0)和半径长/a/
X2+Y2-2bY-2b2=0
x^2+y^2-2by+b^2=3b^2
x^2+(y-b)^2=3b^2
圆心坐标(0,b)和半径长√3/b/