Bonjour
Exercice 2:
1) Factoriser
A = (5x – 2)(4x + 1) + (5x – 2)(x-6)
= (5x - 2) (4x + 1 + x - 6)
= (5x - 2) (5x -5)
= (5x -2) 5(x - 1)
B = (7x-2)2 – (3x + 1)2
= 2[(7x - 2)-(3x + 1)]
= 2(7x - 3x - 2 - 1)
= 2(4x - 3)
2) On pose:
C = (4x – 3)(2x +2) – 5(4x – 3).
a) Développer et réduire C.
C = (4x – 3)(2x +2) – 5(4x – 3).
= 8x² + 8x - 6x - 6 - 20x + 15
= 8x² - 18x + 9
b) Factoriser C.
C = (4x – 3)(2x +2) – 5(4x – 3)
= (4x - 3) [(2x+2) -5]
= (4x -3 ) (2x + 2 - 5)
= (4x - 3) ( 2x -3 )
