Bonjour j'aurais besoin d'aide svp Montrer que 2x^2 - x - 1 = 2(x-1) (x+1/2)

2x² - x - 1 = 2(x-1) (x+1/2)
2x² - x - 1 = 2(x² +1/2x-x-1/2)
2x²-x-1 = 2(x²+1/2x-2/2x-1/2)
2x²-x-1 = 2(x²-1/2x-1/2)
2x²-x-x = 2x²-x-1

2(x-1)(x+1/2) = (2x-2)(x+1/2) = 2x^2 - x -1