Đk: `x + 3 sqrt (x-1) >=0`
`<=> x >=1`.
\(\dfrac{2}{\left(\sqrt{x}+3\right)\left(\sqrt{x}-1\right)}\) có nghĩa khi: \(\left\{{}\begin{matrix}\sqrt{x}+3>0\\\sqrt{x}-1\ne0\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x\ge0\\x\ne1\end{matrix}\right.\)