<div class="exemple">\def{integer a=randint(2..9)}

\def{integer b=randint(2..9)}
\def{text signe1=random(+,-)}
\def{text signe2=random(+,-)}
\def{integer s= \signe1 1*\a+(\signe2 1)*\b}

<center>  
\(\matrix{
        (\signe1 \a)+(\signe2 \b) & = & \s  \\
        (\signe2 \b)+(\signe1 \a) & = & \s }
 )
</center>
</div>
