bjr
a) périmètre du triangle = somme des 3 longueurs (tour du triangle)
P(x) = 3x+2 + x+3 + 2x+1 = 6x + 6
b)
P(x) = 6x + 6 = 18
6x = 18-6
x = 12/6
x = 2
c)
si x = 2
AB = 3x + 2 = 3*2 + 2 = 8
AC = x + 3 = 2+3 = 5
BC = 2x+1 = 2*2+ 1 = 5
=> triangle isocèle puisque AC = BC