Réponses

2014-03-10T15:27:18+01:00
Bonjour,

A =  4 - (sc² + 2sc + 1)
A = 4 - (sc + 1)²
A = 2² - (sc + 1)²
A = [2 - (sc + 1)][2 + (sc + 1)]
A = (2 - sc - 1)(2 + sc + 1)
A = (1 - sc)(3 + sc)
 

2014-03-10T15:28:24+01:00
Sc² + 2sc + 1 = (sc + 1)² donc
A = 4 - (sc +1)²
A = 2² - (sc + 1)² ==> Identité remarquable a² - b² = (a + b)(a - b)
A = (2 + sc + 1)(2 - sc - 1) 
A = (3 + sc)(1 - sc)