Réponse :
1. A(x) = (3x - 5)² + 2x(x + 6) = [(3x-5)(3x-5)] + 4x² + 12x = 9x² - 15x - 15x + 25 + 4x²+ 12x = (9x² + 4x² = 13x²) + (-15x - 15x + 12x = -18x) + 25 = 13x² - 18x + 25
2. B(x) = (2x + 1)(3x - 8) - (x + 4)² = 6x² - 16x + 3x - 8 - [(x + 4)(x + 4)] = 6x² - 13x - 8 -x² - 4x - 4x - 16 = (6x² - x² = 5x²) + (-13x - 8x = -21x) + (-8 -16= - 24) = 5x² - 21x - 24
3. C(x) = (x - 5)(x + 5) + (x + 5)² = x² + 5x - 5x - 25 + (x + 5)(x + 5) = x² - 25 + x² + 5x + 5x + 25 = 2x² + 10x
4. D(x) = (2x + 8)² - (x + 1)(x + 2) = [(2x + 8)(2x + 8)] - x² - 2x - x - 2 = 4x² + 16x + 16x + 64 - x² - 2x - x - 2 = (4x² - x² = 3x²) + (16x + 16x - 2x - x = 29x) + (64 - 2 = 62) = 3x² + 29x + 62
Explications étape par étape
