Réponse :
bonjour
A = (2x - 1)² – (7x - 3)(2x - 1).
A = 4 x² - 4 x + 1 - ( 14 x² - 7 x - 6 x + 3 )
A = 4 x² - 4 x + 1 - 14 x² + 13 x - 3
A = - 10 x² + 9 x - 2
2°) Factoriser A.
A = ( 2 x - 1 ) ( 2 x - 1 - 7 x + 3 )
A = ( 2 x - 1 ) ( - 5 x + 2 )
A = 0 ⇔ x = 1/2 ou 2/5
