calcul A= 6x-(5x+4) B=3x puissance 2 -4) - (3x-2xpuissance 2 ) -15 C= 7(3x+4)-6 D=(x-4)(2x-5) E=(3x-4)puissanse2 F=(2x+5)(3x-1)+5(x-2) G=(3x-5)(2x+1)-(5x-1)(4x-

A = 6x -(5x +4)
6x -5x -4 = x -4
B = 3x² -4 - 3x -2x² -15
x² -19 -3x 
C = 7(3x +4) -6
21x +28 -6
21x +22
D = (x-4)(2x -5)
2x² -5x -8x +20
2x² -13x +20
E = (3x-4)²
9x² -24x +16
F = (2x +5)(3x -1) +5(x-2)
(6x² -2x +15x -5) +5x -10
6x² +13x -5 +5x -10
6x² +18x -15
G = (3x-5)(2x+1) - ( 5x -1)(4x -3)
(6x² +3x -10x -5) - ( +20x² -15x -4x +3)
(6x² -7x -5) - ( 20x² -19x +3)
6x² -7x -5 -20x² +19x -3
-14x² +12x -8