Exercice 1

A = (x +3) (4 + x)

= 4x + x² + 12 + 3x

= x² + 7x + 12

B = (y - 5) (y + 2)

= y² + 2y -5y -10

= y² - 3y - 10

C = (a - 7) (6 - a)

= 6a - a² - 42 + 7a

= - a² + 13a - 42

D = (x +7) (x - 1)

= x² - x + 7x - 7

= x² + 6x - 7

Exercice 2

A = (8b - 1) (-b - 4)

= - 8b² - 32 b + b + 4

= - 8b² - 31b + 4

B = (7 - 5x) (2 - x)

= 14 - 7x - 14x + 5x²

= 5x² - 21x + 14

C = (3x - 1) (5x + 4)

= 15x² + 12x - 5x - 4

= 15x² + 7x - 4

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

= 9 + 6x - 6x - 4x²

= - 4x² + 9