
\documentclass{article}
  \usepackage[width=6cm]{geometry}
  \usepackage{lmodern}
  \usepackage[french]{babel}
  \pagestyle{empty}

\begin{document}
\large Résultats:
\[
\begin{array}{|c @=c|}
   \hline
   \alpha + \beta & 12 \\
   \hline
   \sqrt{\gamma} & 36 \\
   \hline
\end{array}
\]
\end{document}
