\(9x^2-4+\left(x-6\right)\left(3x+2\right)=0\)
\(\Rightarrow\left(3x-2\right)\left(3x+2\right)+\left(x-6\right)\left(3x+2\right)=0\)
\(\Rightarrow\left(3x+2\right)\left(4x-8\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x=-\dfrac{2}{3}\\x=2\end{matrix}\right.\)