The distance from a fixed point (h,k) and variable point (x,y) is given by the distance formula (AKA the Pythagorean Theorem)
A circle is the set of all points (x,y) whose distance from a fixed point (h,k) is a constant, called the radius of the circle. So the distance from the center of a circle to any point on the circle -- the radius of the circle -- is given by
Square both sides to get the equation of the circle in its usual form:
Now just plug in the given numbers: center (h,k) = (-7,-7); radius r=7.
