\documentclass{article}
\usepackage[a4paper,landscape,margin=15mm]{geometry}
\usepackage{amsmath,graphicx}
\newcommand{\exprline}[1]{\par\noindent\begingroup\setbox0=\hbox{$\displaystyle #1$}\ifdim\wd0>\linewidth\resizebox{\linewidth}{!}{\box0}\else\box0\fi\endgroup\par\medskip}
\begin{document}
\noindent\texttt{ELEM\_7\_0198}\\
Version 5.3.1\\
\exprline{a_{0} = \left(mchi_{1} - \frac{mchipm_{1}}{mchipm_{1} \left(- mchipm_{1} - 14.795608864368942\right)}\right)^{3}}
\exprline{a_{1} = \frac{1}{\left(-0.2705410605789888 - \frac{mchipm_{1}^{2} - -0.1104726882190656}{a_{0} mchipm_{1}}\right)^{3}}}
\exprline{a_{2} = mchipm_{1} - \frac{1.985318701882745 \cdot 10^{-5} mchipm_{1}^{4}}{mchipm_{1}} - \frac{mchipm_{1}^{2}}{mchi_{1}^{2}}}
\exprline{a_{3} = \frac{\left(mchipm_{1} + mchipm_{1}\right) \left(- mchipm_{1} - mchipm_{1} \cdot 0.08350758927590293 + 0.38892152913013806\right)^{3}}{mchi_{1} mchipm_{1} \left(mchi_{1} - \frac{mchipm_{1}}{a_{2} \frac{1}{mchipm_{1}}}\right)^{3}}}
\exprline{a_{4} = - \frac{\left(-1\right) 0.04055972416108172 a_{1} mchipm_{1}^{3}}{mchi_{1}^{3}} - mchipm_{1} + \frac{26.510897968433977}{1.873434606670587} - \frac{mchipm_{1}^{3}}{mchipm_{1} \frac{mchipm_{1}}{a_{3}}}}
\exprline{a_{5} = - \frac{- mchipm_{1} + mchipm_{1} \cdot 0.3931877450400627}{mchipm_{1} + mchipm_{1}} - 0.2705410605789888}
\exprline{a_{6} = \frac{\left(mchipm_{1} - 26.511043125521514\right)^{3}}{26.51100404304678 \left(- mchi_{1}^{2} + \frac{26.51100404304678}{mchi_{1}}\right)}}
\exprline{a_{7} = \frac{mchipm_{1}^{2}}{\left(mchipm_{1} - 26.511043125521514\right)^{2} \left(- \frac{mchipm_{1}^{3}}{\left(- mchi_{1} - 0.11680481477984564\right)^{2}} + mchipm_{1}\right)}}
\exprline{a_{8} = \frac{mchi_{1} + 2.3899686946410124}{mchi_{1} \left(mchi_{1} - \frac{mchipm_{1}^{3}}{\left(mchi_{1} - -0.22520722404711024\right)^{2}}\right)}}
\exprline{a_{9} = \frac{mchipm_{1}^{3}}{\left(-0.032661962896898496\right) mchi_{1} mchipm_{1}^{2}} - \frac{mchi_{1}}{a_{8}}}
\exprline{a_{10} = - \frac{0.3435829975042779 \left(- a_{6} + mchi_{1}\right)^{2}}{a_{4} a_{5} \left(- a_{7} - 1.8207158965500432 - \frac{mchipm_{1}}{a_{9}}\right)}}
\exprline{a_{11} = \frac{mchi_{1} mchi_{1}^{3}}{0.5774483375750383 mchi_{1}^{2} mchipm_{1} \frac{- mchipm_{1} - 14.795608864368942}{a_{10}}}}
\exprline{a_{12} = - \frac{mchi_{1}}{a_{11} + mchi_{1}} - 0.43571094061567045 - \frac{26.510897968433977}{mchipm_{1}} - - \frac{0.05460589627929759}{15.27941857975087 \frac{1}{mchi_{1}}}}
\exprline{s = a_{12} \cdot 3.6322438444330944}
\end{document}