Verified answer

1

a) K(5/2;7/2)  formule :demi somme des coordonnées de B et C

b) l = 2/3

c) AK = (9/2;13/2) Soit G(x;y) AG = (x+2;y+3)

    AG = 2/3.AK => (x+2;y+3) = 2/3.(9/2;13/2) = (3;13/3) => x+2 = 3 => x = 1

                                                                                        => y+3 = 13/3 => y = 4/3

donc G = (1;4/3)  

2. GA(-3;-13/3) ; GB = (4;-4/3) ; GC = (-1;17/3)

    GA + GB + GC = (-3+4-1;-13/3-4/3+17/3) = (0;0) coordonnée du vecteur nul

ollé!