ĐKXĐ: x>=3
\(\sqrt{x-3}-2\sqrt{x^2-9}=0\)
=>\(\sqrt{x-3}-2\cdot\sqrt{x-3}\cdot\sqrt{x+3}=0\)
=>\(\sqrt{x-3}\left(1-2\sqrt{x+3}\right)=0\)
=>\(\left[{}\begin{matrix}x-3=0\\2\sqrt{x+3}=1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x-3=0\\x+3=\dfrac{1}{4}\end{matrix}\right.\)
=>\(\left[{}\begin{matrix}x=3\left(nhận\right)\\x=-\dfrac{11}{4}\left(loại\right)\end{matrix}\right.\)