Đáp án+Giải thích các bước giải:
`a) \frac{2\sqrt{2} - 4}{4 - \sqrt{2}}`
`= \frac{2\sqrt{2}(1 - \sqrt{2})}{\sqrt{2}(2\sqrt{2} - 1)}`
`= \frac{2\sqrt{2}(1 - \sqrt{2})}{\sqrt{2}(\sqrt{2} - 1)(2 + \sqrt{2} + 1)}`
`= \frac{-2}{3 + \sqrt{2}}`
`= \frac{2(3 - \sqrt{2})}{7}`
`= \frac{6 - 2\sqrt{2}}{7}`
`b) \frac{\sqrt{15} - 2\sqrt{3}}{2 - \sqrt{5}} - \frac{\sqrt{6} - \sqrt{3}}{\sqrt{2}}`
`= \frac{\sqrt{3}(\sqrt{5} - 2)}{2 - \sqrt{5}} - \frac{\sqrt{12} - \sqrt{6}}{2}`
`= - \sqrt{3} - \frac{\sqrt{12} - \sqrt{6}}{2}`
`= \frac{-2\sqrt{3} - 2\sqrt{3} + \sqrt{6}}{2}`
`= \frac{\sqrt{6} - 4\sqrt{3}}{2}`
