\documentclass{article}
\usepackage{soul}
\begin{document}
\hl{This is a sentence with a citation~\cite{Das}.
\begin{equation}
			2 + 2 = 4
\end{equation}
where $4$ is the number that comes after $3$.}
\begin{thebibliography}{9}
 \bibitem{Das}   Dascioglu A. A, Isle  N.  Bernstein collocation method for solving nonlinear differential equations. Math. Comput. Appl. 2013; 18(3): 293-300.
	\end{thebibliography}
\end{document}