Bonjour ,
E = (3x+5) (2x+4) + (4x+2) (3x+5)
E = 6x² + 12x + 10x + 20 + 12x² + 20x + 6x + 10
E = 18x² + 48x + 30
F = (4x+8) (3x-2) + (4-2x) (5+4x)
F = 12x² - 8x + 24x - 16 + 20 - 16x - 10x - 8x²
F = 4x² - 10x + 4
G = (5x-3) (2x+6) - (6x+5) (4x+2)
G = 10x² + 30x - 6x - 18 - ( 24x² + 12x + 20x + 10 )
G = 10x² + 24x - 18 - 24x² - 12x - 20x - 10
G = -14x² - 8x - 28
H = (4-5x) (-2x+7) - (2x-4) ( 5x-3)
H = -8x + 28 + 10x² - 35x - ( 10x²-6x - 20x + 12 )
H = 10x² - 43x + 28 - 10x² + 6x + 20x - 12
H = - 17x + 12