Réponses

2013-04-18T14:25:49+02:00

E = (2x-5)² -(2x-5)(x-8)

 

= (2x-5)(2x-5)-(x-8)

= (2x-5)(2x-5-x+8)

= (2x-5)(x+3)

 

pour x = -3

E =( -6-5)(-3+3)

E -1 x 0 = 0

pour x = 2/3

E = (4/3-5)(2/3+3)

E = 4/3 -15/3 x 2/3 + 9/3

E = -11/3 x 11/3 = -121/9

(2x-5)(x+3) = 0

 

soit 2x-5 = 0 donc 2x = 5 et x = 5/2

ou x+3 = 0 et x = -3