Réponse :
AB = (xB-xA ; yB-yA) = (4-(-2) ; 2-1) = (6 ; 1)
AC = (xC-xA ; yC-yA) = (-3-4 ; 5-2) = (-7 ; 3)
AM = 3*AB + 2*AC = 3*(6;1) + 2*(-7;3) = (18;3) + (-14;6) = (4;9)