The last very commonly used method for solving quadratics is called the quadratic formula. The quadratic formula is derived from completing the square. In order to use the formula the equation must be written in standard form, so the a, b, and c values can be identified. Watch the following example videos and take notes.
Notice how the value under the radical changed the type of solutions each quadratic had. This value is called the discriminant: b² - 4ac. Watch the following video and copy the chart below.