Bài 2 a làm chi tiết, em mới học ạ

`(\sqrt{7} - 5)/2 - (6 - 2\sqrt{7})/4 + 6/(\sqrt{7} - 2) - 5/(4 + \sqrt{7})`

`= (\sqrt{7} - 5)/2 - (2(3 - \sqrt{7}))/4 + (6(\sqrt{7} + 2))/(7 - 4) - (5(4 - \sqrt{7}))/(16 - 7)`

`= (\sqrt{7} - 5)/2 - (3 - \sqrt{7})/2 + (6(\sqrt{7} + 2))/3 - (5(4 - \sqrt{7}))/9`

`= (\sqrt{7} - 5 - 3 + \sqrt{7})/2 + (6(\sqrt{7} + 2))/3 - (5(4 - \sqrt{7}))/9`

`= (2\sqrt{7} - 8)/2 + (6(\sqrt{7} + 2))/3 - (5(4 - \sqrt{7}))/9`

`= (2(\sqrt{7} - 4))/2 + (6(\sqrt{7} + 2))/3 - (5(4 - \sqrt{7}))/9`

`= \sqrt{7} - 4 + 2(\sqrt{7} + 2) - (5(4 - \sqrt{7}))/9`

`= \sqrt{7} - 4 + 2\sqrt{7} + 4 - (5(4 - \sqrt{7}))/9`

`= 3\sqrt{7} - (5(4 - \sqrt{7}))/9`

`= (27\sqrt{7})/9 - (20 - 5\sqrt{7})/9`

`= (27\sqrt{7} - 20 + 5\sqrt{7})/9`

`= (32\sqrt{7} - 20)/9`