Bonjour,
Exercice 3 :
(a) A = (2x + 1)(3x - 9) + 2(x + 3)(3x - 9)
A = (6x² - 18x + 3x - 9) + (2x + 6)(3x - 9)
A = 6x² - 15x - 9 + (6x² - 18x + 18x - 54)
A = 6x² - 15x - 9 + 6x² - 54
A = 12x² - 15x - 63
(b) B = 9(3x + 1)²
B = 9(9x² + 6x + 1)
B = 81x² + 54x + 9
(c) C = (2x - 5)(2x + 5) - (2 - x)²
C = (4x² - 25) - (4 - 4x + x²)
C = 4x² - 25 - 4 - 4x + x²
C = 5x² - 29 - 4x
Exercice 4 :
(a) D = (2x + 1)(3x - 9) + 2(x + 3)(3x - 9)
D = (3x - 9)[(2x + 1) + 2(x + 3)]
D = (3x - 9)(2x + 1 + 2x + 6)
D = (3x - 9)(4x + 7)
(b) E = 2x² - 20x + 50
E = 2(x² - 10x + 25)
x² - 10x + 25 = (x - 5)²
E = 2(x - 5)²
(c) F = 4x² - 196
F = 4(x² - 48)
