Répondre :
= ( 2x + 1 ) ( x - 1 )
= 2x * x + 2x * (-1) + 1 * x + 1 * (-1)
= 2x^2 - 2x + 1x - 1
= 2x^2 - 1x - 1
= 2x * x + 2x * (-1) + 1 * x + 1 * (-1)
= 2x^2 - 2x + 1x - 1
= 2x^2 - 1x - 1