Bonjour,
E= (x+3)(x-4)+(2x-5)(x+1)
E = x² - 4x + 3x - 12 + 2x² + 2x - 5x - 5
E = x² + 2x² - 4x - 5x + 3x + 2x - 12 - 5
E = 3x² - 6x - 17
F=(2x-7)(3x-5)-(4x+1)(-2x+5)
F = 6x² - 10x - 21x + 35 - (- 8x² + 20x - 2x + 5)
F = 6x² - 10x - 21x + 35 + 8x² - 20x + 2x - 5
F = 6x² + 8x² - 10x - 21x - 20x + 2x + 35 - 5
F = 14x² - 49x + 30