Упростите выражение: a) $$\frac{7}{2}\sqrt{12} + \sqrt{7}(\sqrt{7} - \sqrt{21})$$; б) $$(\sqrt{11} - \sqrt{2})^2$$.

a)$$\frac{7}{2}\sqrt{12} + \sqrt{7}(\sqrt{7} - \sqrt{21}) = \frac{7}{2}\sqrt{4\cdot 3} + 7 - \sqrt{7\cdot 7\cdot 3} = \frac{7}{2} \cdot 2\sqrt{3} + 7 - 7\sqrt{3} = 7\sqrt{3} + 7 - 7\sqrt{3} = 7$$

б) $$(\sqrt{11} - \sqrt{2})^2 = (\sqrt{11})^2 - 2\sqrt{11}\sqrt{2} + (\sqrt{2})^2 = 11 - 2\sqrt{22} + 2 = 13 - 2\sqrt{22}$$