Développons : (a -b)2 (a -b)·(a -b) a·a + a·-b -b·a -b·-b ℹa·a = a2‖a·-b = -a·b‖-b·-b = (-b)2 a2 -ab -ba + (-b)2 ▷Résultat : a2 -2ab + b2