/x+3/=9
x+3=9
=>x=6
Vậy phương trình có 1 no =6
\(\sqrt{\left(x+3\right)^2}=9\Leftrightarrow\left|x+3\right|=9\Leftrightarrow\)\(\left[{}\begin{matrix}x+3=9\\x+3=-9\end{matrix}\right.\)\(\Leftrightarrow\)\(\left[{}\begin{matrix}x=6\\x=-12\end{matrix}\right.\)
Vậy S={-12;6}