When $a ne 0$, there are two solutions to (ax^2 + bx + c = 0) and they are
$$x = {-b pm sqrt{texttip{b^2-4ac}{descriminant}} over 2a}.$$
\begin{aligned}
a&=b+c \\
d+e&=f
\end{aligned}
\bar{y}
\begin{Bmatrix}
a & b \\
c & d
\end{Bmatrix}
\begin{cases}
a &\text{if } b \\
c &\text{if } d
\end{cases}
\cfrac{2}{1+\cfrac{2}{1+\cfrac{2}{1}}}