Bonjour,
On a c=(x-3)2+(4x+1)(x-3)
1) Développer C
c=(x-3)²+(4x+1)(x-3)
c = x² - 6x + 9 + 4x² - 12x + x - 3
c = x² + 4x² - 6x - 12x + x + 9 - 3
c = 5x² - 17x + 6
2) Factoriser C
c = (x-3)²+(4x+1)(x-3)
c = (x - 3) (x - 3 + 4x + 1)
c = (x - 3) (3x - 2)
3) Résoudre l'équation
(x-3)(5x-2)=0
x - 3 = 0 ou 5x - 2 = 0
x = 3 5x = 2
x = 2/5.
