Đáp án+Giải thích các bước giải:
2,
`2\sqrt{3}+\sqrt{(2-\sqrt{3})^2}`
`=2\sqrt{3}+|2-\sqrt{3}|`
`=2\sqrt{3}+2-\sqrt{3}`
`=2+\sqrt{3}`
3,
`\sqrt{7-2\sqrt{10}}-\sqrt{7+2\sqrt{10}}`
`=\sqrt{5-2.\sqrt{5}.\sqrt{2}+2}-\sqrt{5+2.\sqrt{5}.\sqrt{2}+2}`
`=\sqrt{(\sqrt{5}-\sqrt{2})^2}-\sqrt{(\sqrt{5}+\sqrt{2})^2}`
`=|\sqrt{5}-\sqrt{2}|-|\sqrt{5}+\sqrt{2}|`
`=\sqrt{5}-\sqrt{2}-\sqrt{5}-\sqrt{2}`
`=-2\sqrt{2}`
4,
`\sqrt{14-6\sqrt{5}}+\sqrt{14+6\sqrt{5}}`
`=\sqrt{9-2.3.\sqrt{5}+5}+\sqrt{9+2.3.\sqrt{5}+5}`
`=\sqrt{(3-\sqrt{5})^2}+\sqrt{(3+\sqrt{5})^2}`
`=|3-\sqrt{5}|+|3+\sqrt{5}|`
`=3-\sqrt{5}+3+\sqrt{5}`
`=6`
