Sample
When $a \ne 0$, there are two solutions to (ax^2 + bx + c = 0) and they are
$$x = {-b \pm \sqrt{b^2-4ac} \over 2a}.$$
The Lorenz Equations
[\begin{matrix}
\dot{x} & = & \sigma(y-x) \
\dot{y} & = & \rho x - y - xz \
\dot{z} & = & -\beta z + xy
\end{matrix} ]