`6) A = \sqrt{50} - 3\sqrt{8} + \sqrt{3-2\sqrt{2}}`
`= 5\sqrt{2} - 6\sqrt{2} + \sqrt{2} - 1`
`= -1`
Vậy `A = -1`
`7) A = \sqrt{3}\sqrt{3}-3\sqrt{12}+2\sqrt{27}`
`= 3 - 6\sqrt{3} + 6\sqrt{3}`
`= 3`
Vậy `A = 3`
`8) M = 2/(\sqrt{7}-\sqrt{6}) - \sqrt{28} + \sqrt{54}`
`= 2/(\sqrt{7}-\sqrt{6}) - 2\sqrt{7} + 3\sqrt{6}`
`= 2(\sqrt{7}+\sqrt{6}) - 2\sqrt{7} + 3\sqrt{6}`
Vậy `M = 2(\sqrt{7}+\sqrt{6}) - 2\sqrt{7} + 3\sqrt{6}`
`9) 2\sqrt{3} - 5\sqrt{27} + 4\sqrt{12} : \sqrt{8}+4`
`= 2\sqrt{3} - 5\sqrt{27} + 4\sqrt{12} : 2\sqrt{2} + 4`
`= 2\sqrt{3} - 15\sqrt{3} + 8\sqrt{3} : 2\sqrt{2}+4`
`= -5\sqrt{3} : 2\sqrt{2}+4`
`= 5\sqrt{3}(\sqrt{2}-2):4`
