Due to symmetry, x-coordinate of the center is half way between the x-intercepts, i.e.  =  = 6.


Due to the same reason,  y-coordinate of the center is half way between the y-intercepts, i.e.  =  = 2.


So, the center is the point  (6,2).



Now calculate the distance  " r "  from the center to any one of the four given intercept points, using the distance formula.



Then the standard equation of the circle will be


     +  = .