A = 3x (5x + 1) + (5a + 1) (-7x-4)
B = (x - 4) (7 - x) + (x + 3) (7 - x)
C = (2x + 3) (5x - 1) - x (2x + 3)
D = (4x - 5) (x - 3) - (3x - 1) (4x - 5)

A = (5 x + 1) (3 x - 7 x - 4) = (5 x + 1) (- 4 x - 4) B = (7 - x) (x - 4 + x + 3) = (7 - x) (2 x - 1)C = (2 x + 3) (5 x - 1 - x) = (2 x + 3) (4 x - 1) D = (4 x - 5) (x -3 - 3 x + 1) = (4 x - 5) (- 2 x - 2)