The document discusses finding the equation of a circle given its center and radius, or finding the center and radius given the equation. It provides examples of writing the standard equation of a circle (x - h)2 + (y - k)2 = r2 given the center (h, k) and radius r. It also works through examples of finding the center and radius when given the equation of a circle. Finally, it explains how to find the equation of a circle if given its center and that it passes through a specific point.