Bonjour ;
Exercice n° 73 .
Au lieu de souligner le facteur commun , je l'ai mis en gras .
A = 3x - 3 = 3(x - 1) .
B = 4x + 6 = 2 * 2x + 2 * 3 = 2(2x + 3) .
C = 8 + 2x = 2 * 4 + 2x = 2(4 + x) .
D = 7y² - 5y = 7y * y - 5y = y(7y - 5) .
E = 30a + 36a² = 5 * 6a + 6a * 6a = 6a(5 + 6a) .
F = - 9x² - 9 = - 9(x² + 1) .
Exercice n° 74 .
A = (x - 2)(x + 3) + (x - 2)(x + 6)
= (x - 2)(x + 3 + x + 6) = (x - 2)(2x + 9) .
B = (x + 5)(4x - 2) - (x + 5)(9x + 1)
= (x + 5)(4x - 2 - 9x - 1) = (x + 5)(- 5x - 3) = - (x + 5)(5x + 3) .
C = (3x + 8)² - (6x - 7)(3x + 8)
= (3x + 8)(3x + 8) - (6x - 7)(3x + 8) = (3x + 8)(3x + 8 - 6x + 7)
= (3x + 8)(- 3x + 15)
= (3x + 8)( - 3x + 3 * 5)
= 3(3x + 8)(- x + 5) .
