\(\left(3x^2-51\right)^{2n}=\left(-24\right)^{2n}\)
\(\Leftrightarrow3x^2-51=-24\)
\(\Leftrightarrow3x^2=27\)
\(\Leftrightarrow x^2=9\)
\(\Leftrightarrow x=\pm3\)
(3x2 - 51)2n = (-24)2n
=> \(\orbr{\begin{cases}3x^2-51=-24\\3x^2-51=24\end{cases}=>\orbr{\begin{cases}3x^2=27\\3x^2=75\end{cases}}}\)
=>\(\orbr{\begin{cases}x^2=9\\x^2=25\end{cases}=>}\orbr{\begin{cases}x=3\\x=5\end{cases}}\)