Вычислите: a) $$5\sqrt{2} + 23\sqrt{27} - \sqrt{98}$$; б) $$(4\sqrt{3} + \sqrt{27}) \cdot \sqrt{3}$$

а) $$5\sqrt{2} + 23\sqrt{27} - \sqrt{98} = 5\sqrt{2} + 23\sqrt{9\cdot 3} - \sqrt{49\cdot 2} = 5\sqrt{2} + 23 \cdot 3\sqrt{3} - 7\sqrt{2} = -2\sqrt{2} + 69\sqrt{3}$$ <p><strong>Ответ: $$-2\sqrt{2} + 69\sqrt{3}$$</strong></p> б) $$(4\sqrt{3} + \sqrt{27}) \cdot \sqrt{3} = (4\sqrt{3} + \sqrt{9\cdot 3}) \cdot \sqrt{3} = (4\sqrt{3} + 3\sqrt{3}) \cdot \sqrt{3} = 7\sqrt{3} \cdot \sqrt{3} = 7 \cdot 3 = 21$$ <p><strong>Ответ: $$21$$</strong></p>