What is the quadratic formula?

The Quadratic Formula is used when you have a quadratic equation in the form: $${{\mathtt{ax}}}^{{\mathtt{2}}}{\mathtt{\,\small\textbf+\,}}{\mathtt{bx}}{\mathtt{\,\small\textbf+\,}}{\mathtt{c}} = {\mathtt{0}}$$

This page explains the concept more: http://www.purplemath.com/modules/quadform.htm