Réponses

2013-02-19T20:58:40+01:00

a)

E=9-(2x-1)² = 9 - 4x² + 4x - 1 = -4x² +4x + 8

 

b)

E=9-(2x-1)² = 3²-(2x-1)² = (3-2x+1)(3+2x-1) = (4-2x)(2+2x) = 4(2-x)(1+x)

 

c)

E=9 - (2/3 - 3/3)² = 9 - 1/9 = (81-1)/9 = 80/9

 

En espérant t'avoir aidé.

2013-02-19T21:03:23+01:00

E = (9-2x-1)(9+2x-1) =( -2x+8)(8+2x)

E = (2x-1)(3-(2x-1) = (2x-1)(3+2x+1) = (2x-1)(2x+4)

 

pour x = 1/3

E = (2/3-1)(2/3+4)

= (2/3-3/3)(2/3+12/3)

= -1/3 * 14/3 = -14/9