e)
`\sqrt{x^2-2x-3}`
`=\sqrt{x^2+x-3x-3}`
`=\sqrt{x(x+1)-3(x+1)}`
`=\sqrt{(x-3)(x+1)}`
`ĐKXĐ: (x-3)(x+1)>=0`
`=>`$\begin{cases} x-3≥0\\x+1≥0 \end{cases}$ hoặc $\begin{cases} x-3≤0\\x+1≤0 \end{cases}$
`<=>`\(\left[ \begin{array}{l}x≥3\\x≤-1\end{array} \right.\)
f)
`\sqrt{|x-2|-3}`
`ĐKXĐ: |x-2|-3>=0`
`<=>|x-2|>=3`
`<=>`\(\left[ \begin{array}{l}x-2≥3\\x-2≤-3\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x≥5\\x≤-1\end{array} \right.\)
g)
`1/(\sqrt{x+2\sqrt{x-1})`
`ĐKXĐ:` Xét: `2\sqrt{x-1}`
`=>x-1>=0`
`<=>x>=1`
Xét: `\sqrt{x+2\sqrt{x-1}}\ne0` (Luôn đúng)
Vậy: `x>=1`
h)
`-1/(\sqrt{9-12x+4x^2)`
`ĐKXĐ: \sqrt{9-12x+4x^2}=\sqrt{(3-2x)^2}`
`=>(3-2x)^2>=0` (Luôn đúng với `∀x`)
Mà: `(3-2x)^2>0`
`=>(3-2x)^2\ne0`
`<=>3-2x\ne0`
`=>x\ne3/2`
Vậy: `x\ne3/2`
