Ferrari's Method/Also presented as

Ferrari's Method: Also presented as
Ferrari's Method can also be presented in the following form:

Let $P$ be the quartic equation:
 * $x^4 + a_3 x^3 + a_2 x^2 + a_1 x + a_0 = 0$

Then $P$ has solutions:
 * $x = \dfrac {-p \pm \sqrt {p^2 - 8 q} } 4$

where:

where $y_1$ is a real solution to the cubic:
 * $y^3 - a_2 y^2 + \paren {a_1 a_3 - 4 a_0} y - \paren { {a_1}^2 + a_0 {a_3}^2 - 4 a_0 a_2} = 0$