Réponses

Meilleure réponse !
2014-04-17T19:29:02+02:00
D = (5x-3)² - (5x-3)(8x-1)
D = (5x-3)(5x-3) - 
(5x-3)(8x-1)

Tu remarques l'existence d'un facteur commun : 5x-3

D = (5x-3)[5x-3-(8x-1)]
D = (5x-3)(5x-3-8x+1)
D = (5x-3)(-3x-2)

Pour x = 3/5

D = [5*(3/5)-3][-3*(3/5)-2]
D = (15/5 - 3)(-9/5 - 2)
D = (3-3)(-9/5 - 10/5)
D = (0)(-19/5)
D = 0