`\sqrt{4-2\sqrt{3}}-\sqrt{3}`
`=\sqrt{3-2\sqrt{3}+1}-\sqrt{3}`
`=\sqrt{(\sqrt{3}-1)^2}-\sqrt{3}`
`=|\sqrt{3}-1|-\sqrt{3}`
`=\sqrt{3}-1-\sqrt{3}`
`=-1`
................
`\sqrt{11+6\sqrt{2}}-3+\sqrt{2}`
`=\sqrt{9+2\sqrt{3}+2}-3+\sqrt{2}`
`=\sqrt{(3+\sqrt{2})^2}-3+\sqrt{2}`
`=3+\sqrt{2}-3+\sqrt{2}`
`=2\sqrt{2}`
.....
`\sqrt{9x^2}-2x`
`=\sqrt{(3x)^2}-2x`
`=|3x|-2x`
với đk `x < 0`
`=-3x-2x`
`=-5x`
...........
`x-4+\sqrt{16-8x+x^2}`
`=x-4+\sqrt{(x-4)^2}`
Với đk `x > 4`
`=x-4+x-4`
`=2x-8`
