`x/(\sqrt{x}-1)=9/2(ĐK:{(xge0),(xne1):})`
`->2x=9(\sqrt{x}-1)`
`->2x=9\sqrt{x}-9`
`->2x-9\sqrt{x}+9=0`
`->(2\sqrt{x}-3)(\sqrt{x}-3)=0`
`->`\(\left[ \begin{array}{l}2\sqrt{x}=3\\\sqrt{x}=3\end{array} \right.\)
`->`\(\left[ \begin{array}{l}x=\frac{9}{4}\\x=9\end{array} \right.\)
Vậy `S=(9/4;9)`