(sqrt(x) - 3)/(sqrt(x) - 1) = (sqrt(x) - 1)/(sqrt(x) + 3)

$\displaystyle  \begin{array}{{>{\displaystyle}l}}
\frac{\sqrt{x} -3}{\sqrt{x} -1} =\frac{\sqrt{x} -1}{\sqrt{x} +3}\\
\\
DKXD:\ x >0,\ x\neq 1\\
\\
\frac{\sqrt{x} -3}{\sqrt{x} -1} =\frac{\sqrt{x} -1}{\sqrt{x} +3}\\
\\
\Leftrightarrow \frac{\left(\sqrt{x} -3\right)\left[\left(\sqrt{x} -1\right)\left(\sqrt{x} +3\right)\right]}{\sqrt{x} -1} =\frac{\left(\sqrt{x} -1\right)\left[\left(\sqrt{x} -1\right)\left(\sqrt{x} +3\right)\right]}{\sqrt{x} +3}\\
\\
\Leftrightarrow \left(\sqrt{x} -3\right)\left(\sqrt{x} +3\right) =\left(\sqrt{x} -1\right)\left(\sqrt{x} -1\right)\\
\\
\Leftrightarrow x-9=x-2\sqrt{x} +1\\
\\
\Leftrightarrow 2\sqrt{x} =10\\
\\
\Leftrightarrow \sqrt{x} =5\\
\\
\Leftrightarrow x=25\ hoặc\ x=-25\ ( Loại)
\end{array}$

Vậy $\displaystyle x=25$