c) `\sqrt{7+2\sqrt{6}}-\sqrt{7-2\sqrt{6}}`
`=\sqrt{6+2.\sqrt{6}.1+1}-\sqrt{6-2.\sqrt{6}.1+1}`
`=\sqrt{(\sqrt{6}+1)^2}-\sqrt{(\sqrt{6}-1)^2}`
`=|\sqrt{6}+1|-|\sqrt{6}-1|`
`=\sqrt{6}+1-\sqrt{6}+1`
`=2`
Bài `3`:
a) `\sqrt{3x-2}=6` `(x>=2/3)`
⇔`3x-2=36`
⇔`3x=38`
⇔`x=(38)/(3)` `(tm)`
Vậy `S={(38)/(3)}`
b) `\sqrt{(x-1)^2}=5` `(x∈R)`
⇔`|x-1|=5`
⇔\(\left[ \begin{array}{l}x-1=5\\1-x=5\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=6(tm)\\x=-4(tm)\end{array} \right.\)
Vậy `S={6,-4}`
