The equation of a circle with center and radius is
You already have the center given to you, so all you need is the radius. Since a circle is the locus of points equidistant from a point called the center, all you need is the distance from the center to the given point. Reach in the tool box and take out the Distance Formula:
Where and are the coordinates of the given point and the center.
Calculate the radius squared, then substitute , , and into the general equation to get your specific equation. Remember to pay close attention to the signs.
