\def{integer a=randint(1..5)*random(1,-1)}
\def{integer b=randint(1..11)*random(1,-1)}
\def{integer c=randint( 3..15)*random(1,-1)}
\def{integer d=randint( 3..5)*random(1,-1)}
\def{integer ab=\a+\b}
\def{integer ac=\a+\c}
\def{integer bd=\d+\b}
\def{integer abc=\ab+\c}
\def{integer s=\abc+\d}
\def{text a=\a>0? +\a}
\def{text b=\b>0? +\b}
\def{text c=\c>0? +\c}
\def{text d=\d>0? +\d}
\def{text ab=\ab>0? +\ab}
\def{text ac=\ac>0? +\ac}
\def{text abc=\abc>0? +\abc}
<div class="exemple"><center>
\(\begin{array}{ccl}
        A  &=&(\a)+(\b)+(\c)+(\d) \\
        A  &=&(\ab)+(\c)+(\d)  \\
        A  &= & (\abc)+(\d) \\
        A  &=& \s\\
\\
        B & = & ((\a)+(\c))+((\b)+(\d))  \\
        B & = & (\ac)+(\bd)  \\
        B & = & \s
    \end{array})
</center>
</div>
