\(\left(x+3\right)^2\left(x^2+6x+1\right)=9\)
\(\Leftrightarrow\left(x+3\right)^2\left(x^2+6x+9-8\right)=9\)
\(\Leftrightarrow\left(x+3\right)^2\left[\left(x+3\right)^2-8\right]=9\)
\(\Leftrightarrow\left(x+3\right)^4-8\left(x+3\right)^2-9=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\left(x+3\right)^2=-1\left(loai\right)\\\left(x+3\right)^2=9\left(tm\right)\end{matrix}\right.\)
\(\left(x+3\right)^2=9\Leftrightarrow\left[{}\begin{matrix}x+3=3\\x+3=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-6\end{matrix}\right.\) vậy........
