\(\Leftrightarrow\sqrt{9x^2-2}=3x+5\)
\(\Leftrightarrow\left\{{}\begin{matrix}3x+5\ge0\\9x^2-2=\left(3x+5\right)^2\end{matrix}\right.\)
\(\Leftrightarrow\left\{{}\begin{matrix}x\ge-\dfrac{5}{3}\\9x^2-2=9x^2+30x+25\end{matrix}\right.\)
\(\Rightarrow x=-\dfrac{9}{10}\) (thỏa mãn)