a) \(\sqrt{x^2}=9\)
\(\Leftrightarrow\left|x\right|=9\)\(\Leftrightarrow\left[{}\begin{matrix}x=9\\x=-9\end{matrix}\right.\)
b) \(\Leftrightarrow\sqrt{\left(x-2\right)^2}=8\)
\(\Leftrightarrow\left|x-2\right|=8\)
\(\Leftrightarrow\left[{}\begin{matrix}x-2=8\\x-2=-8\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=10\\x=-6\end{matrix}\right.\)
c) \(ĐK:x\ge3\)
\(\Leftrightarrow\sqrt{\left(x-5\right)^2}=x-3\)
\(\Leftrightarrow\left|x-5\right|=x-3\)
\(\Leftrightarrow\left[{}\begin{matrix}x-5=x-3\left(x\ge5\right)\\x-5=3-x\left(3\le x< 5\right)\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}-5=-3\left(VLý\right)\\x=4\left(tm\right)\end{matrix}\right.\)
