Bonjour,
F = (3 - x) (2x + 4) - (2x + 4) (5x - 2)
F = 3 * 2x + 3 * 4 - x * 2x - x * 4 - (2x * 5x + 2x * (-2) + 4 * 5x + 4 * (-2))
F = 6x + 12 - 2x² - 4x - (10x² - 4x + 20x - 8)
F = 6x + 12 - 2x² - 4x - 10x² + 4x - 20x + 8
F = -2x² - 10x² + 6x + 4x - 4x - 20x + 12 + 8
F = -12x² - 14x + 20
