\(\left(x^2-9\right)^2=12x+1\)
\(\Leftrightarrow x^4-18x+81=12x+1\)
\(\Leftrightarrow x^4-18x-12x=-81+1\)
\(\Leftrightarrow x^4-30x=-80\)
\(\Leftrightarrow x\left(x^3-30\right)=-80\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-80\\x^3-30=-80\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-80\\x^3=-50\end{matrix}\right.\)