F1 (x) = x² + 3 → OUI, a = 1 | b = 0 | c = 3.
F2 (x) = (x - 1) + 2 = x - 1 + 2 = x + 1 → NON, car a = 0.
F3 (x) = (x + V5)² = x² + 2xV5 + 5 → OUI, a = 1 | b = 2V5 | c = 5.
F4 (x) = (x + 1)² - (x - 2)² = x² + 2x + 1 - (x² - 4x + 4) = x² + 2x + 1 - x² + 4x - 4 = 6x - 3 → NON, car a = 0.