\(\Leftrightarrow\left|x-3\right|=9\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=9\left(x\ge3\right)\\x-3=-9\left(x< 3\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=12\left(TM\right)\\x=-6\left(TM\right)\end{matrix}\right.\)
Vậy pt có nghiệm là \(S=\left\{-6;12\right\}\)