Bonjour ;
Exercice n° 3 .
B = (2x + 3)(4x + 6) = 8x² + 12x + 12x + 18 = 8x² + 24x + 18 .
C = (5x - 3)(3x - 8) = 14x² - 40x - 9x + 24 = 15x² - 49x + 24 .
D = (2x + 3)(5x + 2) + (2x - 4)(x + 1)
= 10x² + 4x + 15x + 6 + 2x² + 2x - 4x - 4
= 12x² + 17x + 2 .
Exercice n° 4 .
E = 2x² + 7x = x(2x + 7) .
F = (x - 5)(2x - 3) - (x - 5)(x + 12)
= (x - 5)(2x - 3 - x - 12)
= (x - 5)(x - 15) .
G = (x - 2)² + (x - 2)(2x + 9)
= (x - 2)(x - 2 + 2x + 9)
= (x - 2)(3x + 7) .