1. Factoriser
B = (7x - 2)² – (3x + 1)²
B = [(7x - 2) - (3x + 1)] [(7x - 2) + (3x + 1)]
B = (7x - 2 - 3x - 1)(7x - 2 + 3x + 1)
B = (4x - 3)(10x - 1)
2.a. Développer et réduire C
C = (4x - 3)(2x +2) - 5(4x - 3)
C = 4x*2x + 4x*2 - 3*2x - 3*2 - 5*4x - 5*-3
C = 8x² + 8x - 6x - 6 - 20x + 15
C = 8x² - 18x + 9
2.b. Factoriser C
C = (4x - 3)(2x +2) - 5(4x - 3)
C = (4x - 3) [(2x + 2) - 5]
C = (4x - 3) (2x - 3)
