The Quadratic Formula is a result of Completing the Square using the coefficients a, b, and c of a quadratic equation. The most memorable formula for most students is the quadratic equation.
Move the slider down to expose an algebraic explanation of the Method of Completing the Square.

This applet can be used by teachers in a demonstration mode in the classroom or teachers can have students load it on their own computers as a worksheet to be completed for a grade.