bjr
somme 1er colonne
= - 9x - 3 + (x + 3)
soit = - 9x + x - 3 + 3
= - 8x
somme 2eme colonne
= - x + 7 + (-7x - 2)
soit = - x - 7x + 7 - 2
= - 8x + 5
etc.. :)
