$
\Large\frac{{b^2 }}{{4a^2 }} - \frac{c}{a} = \frac{{b^2 }}{{4a^2 }} - \frac{{4ac}}{{4a^2 }} = \frac{{b^2 - 4ac}}{{4a^2 }}
$
$
\Large\begin{array}{l}
x_{1,2} = - \frac{b}{{2a}} \pm \sqrt {\frac{{b^2 }}{{4a^2 }} - \frac{c}{a}} = \\
x_{1,2} = - \frac{b}{{2a}} \pm \sqrt {\frac{{b^2 - 4ac}}{{4a^2 }}} = \\
x_{1,2} = - \frac{b}{{2a}} \pm \frac{{\sqrt {b^2 - 4ac} }}{{2a}} = \\
x_{1,2} = \frac{{ - b \pm \sqrt {b^2 - 4ac} }}{{2a}} \\
\end{array}
$