Réponse :
Exercice 4:
1.
P = (3x-7)² + (3x-7)(5x+3)
= (3x-7) ( (3x-7)+(5x+3) )
= (3x-7) ( 15x² + 9x - 35x - 21 )
P = (3x-7) ( 15x² - 26x - 2 )
Si x=7/3
Alors :
3x - 7 = 3* 7/3 -7
=21/3-7
=7-7 = 0
Donc :
P = (3x-7) ( 15x² - 26x - 2 )
= 0 ( 15x² - 26x - 2 )
P = 0
2.
E = (6a-4)² - (5a+8)
= 36a² - 48a +16 - 5a +8
E = 36a² - 53a +24
Si a=0
E = 0 - 0 +24
donc
E=24
