Purple Math
Purplemath: Completing the Square: Solving Quadratic Equations
Purplemath gives several examples which clearly show the process of completing the square to find the maximum and minimum solutions to a quadratic equation.
Khan Academy
Khan Academy: Completing the Square (Intro)
Try these multiple-choice practice problems on completing the square.
Khan Academy
Khan Academy: Solving Quadratics by Completing the Square
Practice some multiple-choice problems solving quadratics by completing the square.
Khan Academy
Khan Academy: Completing the Square
Solve quadratic equations of the form ax^2+bx+c by completing the square. Students receive immediate feedback and have the opportunity to try questions repeatedly, watch a video, or receive hints.
CK-12 Foundation
Ck 12: Algebra: Completing the Square
[Free Registration/Login may be required to access all resource tools.] Learn how to complete the square in order to solve quadratic equations.