By completing the square the quadratic equation can be made into

x^2+\frac{b}{a}x&=-\frac{c}{a} (x+\frac{b}{2a})^2&=\frac{b^2}{4a^2}-\frac{c}{a}(x+\frac{b}{2a})^2&=\frac{b^2-4ac}{4a^2} x+\frac{b}{2a}&=\pm \frac{sqrt{b^2-4ac}}{2a}x&=\frac{-b\pm \sqrt{b^2-4ac}}{2a}\end{align}" border=0 align=absmiddle>

The videos below show you how to practically use the quadratic formula to solve quadratic equation.