bonjour aidez moi SVP merci

Exercice 6
A = (x-5)(3x+5) + (4x -2)(5x-2) 
(3x² +5x -15x -25) + ( 20x² -8x -10x +4)
3x² -10x -25 +20x² -18x +4
+23x² -28x -21

B = (3x +2)(2x-5) - ( 6x -5)(4x +2)
(6x² -15x +4x -10) - ( 24x² +12x -20x -10)
6x² -11x -10 - (24x² -8x -10)
6x² -11x -10 -24x² +8x +10
-18x² -3x

C = (4x-5)(2x-5) - (4x +1)(2x-3)
(8x² -20x -10x +25) - ( 8x² -12x +2x -3)
8x² -30x +25 - ( 8x² -10x -3)
8x² -30x +25 -8x² +10x +3
-20x +28