Verified answer

Bonjour,

1) Développer puis réduire E :

E = (7x - 3)² - (3 + 2x) (7x - 3)

E = 49x² - 42x + 9 - (21x - 9 + 14x² - 6x)

E = 49x² - 42x + 9 - 21x + 9 - 14x² + 6x

E = 49x² - 14x² - 42x - 21x + 6x + 9 + 9

E = 35x² - 57x + 18

2) Factoriser E :

E = (7x - 3)² - (3 + 2x) (7x - 3)

E = (7x - 3) [(7x - 3) - (3 + 2x)]

E = (7x - 3) (7x - 3 - 3 - 2x)

E = (7x - 3) (5x - 6)