4.tex

\documentclass[landscape, 12pt]{report}
\usepackage{graphicx}
\pagestyle{empty}

\begin{document}
\noindent Here is some text
\begin{equation}
\resizebox{1.0 \textwidth}{!}
{
    $ a + b $
}
\end{equation}
and here is some more.
\end{document}