\documentclass[a4paper]{article}
\begin{document}
\begin{eqnarray*}
f (x)
 & = & \sqrt{ax^{2} + bx + c} \\
a
 & > & 0 \\
D
 & = & b^{2} - 4ac \, \, \, = \, \, \, 0 \\
\end{eqnarray*}
\newpage
\begin{eqnarray*}
f (x)
 & = & g (h (x)) \\
\end{eqnarray*}
\newpage
\begin{eqnarray*}
f^{\prime} (x)
 & = & g^{\prime} (h (x)) h^{\prime} (x) \\
\end{eqnarray*}
\newpage
\begin{eqnarray*}
p
 & = & \frac{- b + \sqrt{b^{2} - 4ac}}{2a} \\
& = & \frac{- b + \sqrt{0}}{2a} \\
& = & - \frac{b}{2a} \\
\end{eqnarray*}
\newpage
\begin{eqnarray*}
q
 & = & \frac{- b - \sqrt{b^{2} - 4ac}}{2a} \\
& = & \frac{- b - \sqrt{0}}{2a} \\
& = & - \frac{b}{2a} \\
\end{eqnarray*}
\newpage
\begin{eqnarray*}
F (x)
 & = & \int \sqrt{ax^{2} + bx + c} \, \mbox{d}x \\
& = & \int \sqrt{a (x - p) (x - q)} \, \mbox{d}x \\
& = & \int \sqrt{a \left ( x + \frac{b}{2a} \right ) \left ( x + \frac{b}{2a} \right )} \, \mbox{d}x \\
& = & \int \sqrt{a \left ( x + \frac{b}{2a} \right )^{2}} \, \mbox{d}x \\
& = & \sqrt{a} \int \left ( x + \frac{b}{2a} \right ) \, \mbox{d}x \\
& = & \sqrt{a} \left ( \frac{1}{2} x^{2} + \frac{b}{2a} x \right ) + C \\
& = & \frac{1}{2} \sqrt{a} x^{2} + \frac{b}{2 \sqrt{a}} x + C \\
\end{eqnarray*}
\newpage
\begin{eqnarray*}
f (x)
 & = & \frac{\mbox{d}(F (x))}{\mbox{d}x} \\
& = & \frac{\mbox{d}}{\mbox{d}x} \left ( \frac{1}{2} \sqrt{a} x^{2} + \frac{b}{2 \sqrt{a}} x + C \right ) \\
& = & \frac{1}{2} \sqrt{a} \cdot 2x + \frac{b}{2 \sqrt{a}} + 0 \\
& = & \sqrt{a} x + \frac{b}{2 \sqrt{a}} \\
& = & \sqrt{\left ( \sqrt{a} x + \frac{b}{2 \sqrt{a}} \right )^{2}} \\
& = & \sqrt{ax^{2} + 2 \sqrt{a} x \frac{b}{2 \sqrt{a}} + \frac{b^{2}}{4a}} \\
& = & \sqrt{ax^{2} + bx + \frac{4ac}{4a}} \\
& = & \sqrt{ax^{2} + bx + c} \\
\end{eqnarray*}
\newpage
\begin{eqnarray*}
F (x)
 & = & + \frac{1}{2} \sqrt{a} x^{2} + \frac{b}{2 \sqrt{a}} x + C \qquad x \, > \, - \frac{b}{2a} \\
& = & - \frac{1}{2} \sqrt{a} x^{2} - \frac{b}{2 \sqrt{a}} x + C \qquad x \, < \, - \frac{b}{2a} \\
\end{eqnarray*}
\newpage
\begin{eqnarray*}
F (x)
 & = & + \frac{1}{2} \sqrt{a} x^{2} + \frac{b}{2 \sqrt{a}} x + C \qquad x \, > \, - \frac{b}{2a} \\
& = & - \frac{1}{2} \sqrt{a} x^{2} - \frac{b}{2 \sqrt{a}} x + C \qquad x \, < \, - \frac{b}{2a} \\
\end{eqnarray*}
\end{document}
