# Application of Completing the Square

Completing the square is used to find the radius and center of circles. The standard form for a circle is \(ax^2+by^2+cx+dy+e =0\). To find the radius and center of the circle the equation will need to be in the form \((x-h)^2+(y-k)^2 = r^2\) where center is (\(h,k\)) and the radius is \(r\).

Use this link to watch the video to help with the next task. After watching the video, return to this page by using the back arrow.

Features of a circle from its expanded equation | Khan Academy

Completing the square is also used to find the center and vertices of an ellipse.