\(\left(x^2-9\right)\left(3x+2\right)=\left(9-x^2\right)\left(3-2x\right)\)
\(\Leftrightarrow\left(x^2-9\right)\left(3x+2\right)+\left(x^2-9\right)\left(3-2x\right)=0\)
\(\Leftrightarrow\left(x^2-9\right)\left(3x+2+3-2x\right)=0\)
\(\Leftrightarrow\left(x^2-9\right)\left(x+5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-3\\x=-5\end{matrix}\right.\)