Réponses

2014-05-19T18:09:01+02:00
Bonsoir

C = (x-1)(2x +3) + (x-1)²

Développement
C = 2x² + 3x - 2x - 3 + x² - 2x +1
C = 3x² -x -2

factorisation
C = (x-1)(2x+3+x-1)
C = (x-1)(3x +2)

Pour x = √2
C = (√2 -1)(3√2 +2)
c = 6 + 2√2 - 3√2 - 2
C = 4 - √2

(x-1)(3x+2) = 0

soit x -1 = 0 et x = 1
soit 3x +2 = 0
3x = -2
x = - 2/3