A= (12x+7)-(11-5x)(12x+7)
= 12 x + 7 - ( 132 x + 77 - 60 x² - 35 x)
= 12 x + 7 - 132 x - 77 + 60 x² + 35 x
= 60 x² - 85 x - 70
calculer A pour x= -5/12
A = 60 ( - 5/12 )² - 85 ( - 5/12 ) - 70
= 60 * 25/144 + 425/12 - 70
= 300/144 + 5 100 /144 - 10 080 /144
= 4 680 /144
= 65/2
