如下
(2x-4+1)^2+(2y-3)^2 =4 (2x-3)^2+(2y-3)^2 =4 4(x- 3/2)^2+4(y- 3/2)^2 =4 (x-3/2)^2+(y- 3/2)^2 =1 圆心=(3/2, 3/2) 半径=1
