\(x-5.\sqrt{x}=0\)
\(\Leftrightarrow\sqrt{x}.\left(\sqrt{x}-5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x}=0\\\sqrt{x}-5=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\\sqrt{x}=5\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=25\end{matrix}\right.\)
Vậy \(x\in\left\{0;25\right\}\)