Exercice 31 :
A = (x + 4) (x - 6) + (- 1 + x) (x - 6)
A = (x - 6) [(x + 4) + (- 1 + x)]
A = (x - 6) (x + 4 - 1 + x)
A = (x - 6) (2x + 3)
B = (7x - 4) (x + 4) + (7x - 4) (7x - 1)
B = (7x - 4) [(x + 4) + (7x - 1)]
B = (7x - 4) (x + 4 + 7x - 1)
B = (7x - 4) (8x + 3)
C = (x + 1) (5x - 6) - (5x - 6) (- 1 + 4x)
C = (5x - 6) [(x + 1) - (- 1 + 4x)]
C = (5x - 6) (x + 1 + 1 - 4x)
C = (5x - 6) (- 3x + 2)
D = (3x + 8) (x + 4) - (x - 1) (3x + 8)
D = (3x + 8) [(x + 4) - (x - 1)]
D = (3x + 8) (x + 4 - x + 1)
D = (3x + 8) * 5