\documentclass[a4paper]{article}
\begin{document}
\begin{eqnarray*}
\mbox{(1)} \qquad \beta
 & = & \frac{v}{c} \\
\end{eqnarray*}
\newpage
\begin{eqnarray*}
\mbox{(2)} \qquad E
 & = & m_{0} c^{2} \left ( \frac{1}{\sqrt{1 - \beta^{2}}} - 1 \right ) \\
\end{eqnarray*}
\newpage
\begin{eqnarray*}
E
 & = & m_{0} c^{2} \left ( \frac{1}{\sqrt{1 - \beta^{2}}} - 1 \right ) \\
\frac{E}{m_{0} c^{2}}
 & = & \frac{1}{\sqrt{1 - \beta^{2}}} - 1 \\
\frac{E}{m_{0} c^{2}} + 1
 & = & \frac{1}{\sqrt{1 - \beta^{2}}} \\
\left ( \frac{E}{m_{0} c^{2}} + 1 \right )^{-1}
 & = & \sqrt{1 - \beta^{2}} \\
\left ( \frac{E}{m_{0} c^{2}} + 1 \right )^{-2}
 & = & 1 - \beta^{2} \\
\beta^{2}
 & = & 1 - \left ( \frac{E}{m_{0} c^{2}} + 1 \right )^{-2} \\
\beta
 & = & \sqrt{1 - \left ( \frac{E}{m_{0} c^{2}} + 1 \right )^{-2}} \\
v
 & = & c \sqrt{1 - \left ( \frac{E}{m_{0} c^{2}} + 1 \right )^{-2}} \\
\end{eqnarray*}
\end{document}
