You can put this solution on YOUR website! Think about the circle containing those three points, and that the three points form a triangle. The perpendicular bisectors of the three segments will intersect in the CENTER of the circle. Can you find this center point?
Now, use this center point; and pick ANY point on the circle. Use the Distance Formula to find the size of the circle's radius.
Next, just put the needed values into the standard form equation for a circle. with center (h,k) and radius r.