When $a \ne 0$, there are two solutions to $(ax^2 + bx + c = 0)$ and they are
$$ x = {-b \pm \sqrt{b^2-4ac} \over 2a} $$
$$
\left\lbrace
\begin{aligned}
& E=mc^2\\
& F=ma
\end{aligned}
\right\rbrace
$$
The Cauchy-Schwarz Inequality
$$\left( \sum_{k=1}^n a_k b_k \right)^2 \leq \left( \sum_{k=1}^n a_k^2 \right) \left( \sum_{k=1}^n b_k^2 \right)$$