Explications étape par étape :
A = 16x + 24x + 9
⇔ A = 40x + 9
B = ( 2x - 1 )² - 4 a² - b² = ( a - b ) ( a + b )
⇔ B = ( 2x - 1 - 2 ) ( 2x - 1 + 2 )
⇔ B = ( 2x - 3 ) ( 2x + 1 )
⇔ B = 4x² + 2x - 6x - 3
⇔ B = 4x² - 4x - 3
C = ( 3x + 1 ) ( 2 - 5x ) - ( 5 + x ) ( 2 - 5x )
⇔ C = ( 2 - 5x ) [ ( 3x + 1 ) - ( 5 + x ) ]
⇔ C = ( 2 - 5x ) ( 3x + 1 - 5 - x )
⇔ C = ( - 5x +2 ) ( 2x - 4 )
⇔ C = -10x² + 20x + 4x - 8
⇔ C = -10x² + 24x - 8
