Bonjour,
Factoriser :
(2x+3)²-(5x-4)²
= (2x + 3) (2x + 3) - (5x - 4) (5x - 4)
= (2x + 3 + 5x - 4) (2x + 3 - 5x + 4)
= (7x - 1) (- 3x + 7)
