1. Calculer et simplifier: A = \sqrt{9} = 3 B = (\sqrt{7})^2 = 7 C = 5\sqrt{2} - \sqrt{18} = 5\sqrt{2} - \sqrt{9 \times 2} = 5\sqrt{2} - 3\sqrt{2} = (5 - 3)\sqrt{2} = 2\sqrt{2} D = \sqrt{\frac{12}{3}} = \sqrt{4} = 2 2. Rendre rationnel les dénominateurs: E = \frac{1}{\sqrt{3}} \times \frac{\sqrt{3}}{\sqrt{3}} = \frac{\cancel{1} \times \sqrt{3}}{\cancel{\sqrt{3}} \times \sqrt{3}} = \frac{\sqrt{3}}{3} F = \frac{2}{\sqrt{8+1}} = \frac{2}{\sqrt{9}} = \frac{2}{3} 3. Développer et simplifier: G = (\sqrt{2} + 5)^2 = (\sqrt{2})^2 + 2 \times \sqrt{2} \times 5 + 5^2 = 2 + 10\sqrt{2} + 25 = 27 + 10\sqrt{2} H = (\sqrt{7} + 1)(\sqrt{7} - 1) = (\sqrt{7})^2 - 1^2 = 7 - 1 = 6 4. Factoriser: I = x^2 - 10x + 25 = (x - 5)^2 K = x^2 - 4 = (x - 2)(x + 2) 5. Écriture scientifique: 0,00012 = 1.2 \times 10^{-4} 5200 \times 10^{-3} = 5.2 \times 10^{0} = 5.2