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\begin{document}
\tableofcontents
\chapter{Opérations sur les nombres relatifs}
\begin{center}
\small{\textit{Pré-requis : $\emptyset$}}
\end{center}
\section{Additionner des relatifs entre eux}
\uuline{Méthode de calcul:} Pour additionner deux nombres relatifs :

\vspace*{1cm}

\noindent
 \begin{tabular}{|l|l|}
\noindent\hspace{2cm} \textbf{S'ils sont de même signe} \hspace{2cm} & \noindent\hspace{2cm} \textbf{S'ils sont de signes contraires} \hspace{2cm} \\
$\rightarrow$ On les \ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots sans le signe & $\rightarrow$ On les \ldots\ldots\ldots\ldots\ldots\ldots\ldots\ldots sans les signes\\
$\rightarrow$ On met le signe \dotfill & $\rightarrow$ On met le signe \dotfill \\
\end{tabular}

\end{document}