Đáp án:
Giải thích các bước giải:
Z) `\sqrt{(\sqrt{7}-2)^2}+\sqrt{(\sqrt{7}-5)^2}`
`=|\sqrt{7}-2|+|\sqrt{7}-5|`
`=\sqrt{7}-2+5-\sqrt{7}`
`=3`
II) `\sqrt{23+8\sqrt{7}}-\sqrt{7}`
`=\sqrt{(\sqrt{7}+4)^2}-\sqrt{7}`
`=|\sqrt{7}+4|-\sqrt{7}`
`=4+\sqrt{7}-\sqrt{7}`
`=4`
IV) `\sqrt{11+2\sqrt{30}}-\sqrt{11-2\sqrt{30}}`
`=\sqrt{(\sqrt{5}+\sqrt{6})^2}-\sqrt{(\sqrt{5}-\sqrt{6})^2}`
`=|\sqrt{5}+\sqrt{6}|-|\sqrt{5}-\sqrt{6}|`
`=\sqrt{5}+\sqrt{6}+\sqrt{5}-\sqrt{6}`
`=2\sqrt{5}`
