Bonjour,
On a u3 = 3^2 - 3 = 9 - 3 = 6
u5 = 5^2 - 5 = 25 - 5= 20
u15 = 15^2 - 15 = 225 - 15 = 210
Réponse:
u3= 9-3=6
u5=25-5=20
u15=225-15=210