ĐK: \(\left[{}\begin{matrix}x\le-3\\x\ge3\end{matrix}\right.\)
\(\sqrt{x+3}-2\sqrt{x^2-9}=0\)
\(\Leftrightarrow\sqrt{x+3}-2\sqrt{x+3}\cdot\sqrt{x-3}=0\)
\(\Leftrightarrow\sqrt{x+3}\left(1-2\sqrt{x-3}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\sqrt{x+3}=0\\2\sqrt{x-3}=1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x+3=0\\x-3=\frac{1}{4}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-3\\x=\frac{13}{4}\end{matrix}\right.\)( thỏa )
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