\documentclass{imsproc}
\usepackage[extrafootnotefeatures]{xepersian}
\paragraphfootnotes

\begin{document}

\begin{equation*}
\hat{\beta}=\frac{(s_{gg}-\lambda s_{ww})+[(s_{gg}-\lambda s_{ww})^2+4\lambda(s_{wg}-\sigma_{em}^2)]^{\frac{1}{2}}{2(s_{wg}-\sigma_{em})}
\end{equation*}
\end{document}