%@P:exocorcp %@Auteur: d'après IREM Strasbourg \begin{center} \begin{tabular}{|>{\columncolor[rgb]{1,1,0}}*{8}{c|}} \hline \rowcolor{yellow}$\times$&&&&\phantom{15}&8&&\\ \hline &&8&&&&&20\\ \hline &&&&&16&&\\ \hline \phantom{15}&&&15&&&20&\\ \hline &&&9&&&&\\ \hline 7&49&&&7&&&\\ \hline &&18&&&72&&\\ \hline &&&&&&24&\\ \hline \end{tabular} \end{center} %@Correction: \begin{center} \begin{tabular}{|>{\columncolor[rgb]{1,1,0}}*{8}{c|}} \hline \rowcolor{yellow}$\times$&\opcopy{7}{a1}\textcolor{red}{\opprint{a1}}&\opcopy{2}{a2}\textcolor{red}{\opprint{a2}}&\opcopy{3}{a3}\textcolor{red}{\opprint{a3}}&\opcopy{1}{a4}\textcolor{red}{\opprint{a4}}&\opcopy{8}{a5}\opprint{a5}&\opcopy{4}{a6}\textcolor{red}{\opprint{a6}}&\opcopy{5}{a7}\textcolor{red}{\opprint{a7}}\\ \hline \opcopy{4}{b1}\textcolor{red}{\opprint{b1}}&\opmul*{b1}{a1}{a}\textcolor{red}{\opprint{a}}&\opmul*{b1}{a2}{a}\opprint{a}&\opmul*{b1}{a3}{a}\textcolor{red}{\opprint{a}}&\opmul*{b1}{a4}{a}\textcolor{red}{\opprint{a}}&\opmul*{b1}{a5}{a}\textcolor{red}{\opprint{a}}&\opmul*{b1}{a6}{a}\textcolor{red}{\opprint{a}}&\opmul*{b1}{a7}{a}\opprint{a}\\ \hline \opcopy{2}{b2}\textcolor{red}{\opprint{b2}}&\opmul*{b2}{a1}{a}\textcolor{red}{\opprint{a}}&\opmul*{b2}{a2}{a}\textcolor{red}{\opprint{a}}&\opmul*{b2}{a3}{a}\textcolor{red}{\opprint{a}}&\opmul*{b2}{a4}{a}\textcolor{red}{\opprint{a}}&\opmul*{b2}{a5}{a}\opprint{a}&\opmul*{b2}{a6}{a}\textcolor{red}{\opprint{a}}&\opmul*{b2}{a7}{a}\textcolor{red}{\opprint{a}}\\ \hline \opcopy{5}{b3}\textcolor{red}{\opprint{b3}}&\opmul*{b3}{a1}{a}\textcolor{red}{\opprint{a}}&\opmul*{b3}{a2}{a}\textcolor{red}{\opprint{a}}&\opmul*{b3}{a3}{a}\opprint{a}&\opmul*{b3}{a4}{a}\textcolor{red}{\opprint{a}}&\opmul*{b3}{a5}{a}\textcolor{red}{\opprint{a}}&\opmul*{b3}{a6}{a}\opprint{a}&\opmul*{b3}{a7}{a}\textcolor{red}{\opprint{a}}\\ \hline \opcopy{3}{b4}\textcolor{red}{\opprint{b4}}&\opmul*{b4}{a1}{a}\textcolor{red}{\opprint{a}}&\opmul*{b4}{a2}{a}\textcolor{red}{\opprint{a}}&\opmul*{b4}{a3}{a}\opprint{a}&\opmul*{b4}{a4}{a}\textcolor{red}{\opprint{a}}&\opmul*{b4}{a5}{a}\textcolor{red}{\opprint{a}}&\opmul*{b4}{a6}{a}\textcolor{red}{\opprint{a}}&\opmul*{b4}{a7}{a}\textcolor{red}{\opprint{a}}\\ \hline \opcopy{7}{b5}\opprint{b5}&\opmul*{b5}{a1}{a}\opprint{a}&\opmul*{b5}{a2}{a}\textcolor{red}{\opprint{a}}&\opmul*{b5}{a3}{a}\textcolor{red}{\opprint{a}}&\opmul*{b5}{a4}{a}\opprint{a}&\opmul*{b5}{a5}{a}\textcolor{red}{\opprint{a}}&\opmul*{b5}{a6}{a}\textcolor{red}{\opprint{a}}&\opmul*{b5}{a7}{a}\textcolor{red}{\opprint{a}}\\ \hline \opcopy{9}{b6}\textcolor{red}{\opprint{b6}}&\opmul*{b6}{a1}{a}\textcolor{red}{\opprint{a}}&\opmul*{b6}{a2}{a}\opprint{a}&\opmul*{b6}{a3}{a}\textcolor{red}{\opprint{a}}&\opmul*{b6}{a4}{a}\textcolor{red}{\opprint{a}}&\opmul*{b6}{a5}{a}\opprint{a}&\opmul*{b6}{a6}{a}\textcolor{red}{\opprint{a}}&\opmul*{b6}{a7}{a}\textcolor{red}{\opprint{a}}\\ \hline \opcopy{6}{b7}\textcolor{red}{\opprint{b7}}&\opmul*{b7}{a1}{a}\textcolor{red}{\opprint{a}}&\opmul*{b7}{a2}{a}\textcolor{red}{\opprint{a}}&\opmul*{b7}{a3}{a}\textcolor{red}{\opprint{a}}&\opmul*{b7}{a4}{a}\textcolor{red}{\opprint{a}}&\opmul*{b7}{a5}{a}\textcolor{red}{\opprint{a}}&\opmul*{b7}{a6}{a}\opprint{a}&\opmul*{b7}{a7}{a}\textcolor{red}{\opprint{a}}\\ \hline \end{tabular} \end{center}