Bonjour,
Exercice 2. 1 :
AB + FA = FA + AB = FB
FD + EB = FD + DC = FC
AE + GB + DH = AE + EH + HB = AB
2)
CH + GE = CH + HD = CD car GE = HD
AE + CB + EB = AE + EF + FA = vecteur nul
BA + DC - FE = DE + EB + BA = DA
AC + EB = FD + DC = FC
Bon confinement