\(\Leftrightarrow\left(3x^2+7x+4\right)\left(36x^2+84x+49\right)=6\)
Đặt \(3x^2+7x=a\Rightarrow36x^2+84x=12a\)
\(\left(a+4\right)\left(12a+49\right)-6=0\)
\(\Leftrightarrow12a^2+97a+190=0\)
\(\Leftrightarrow\left[{}\begin{matrix}a=-\frac{10}{3}\\a=-\frac{19}{4}\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}3x^2+7x+\frac{10}{3}=0\\3x^2+7x+\frac{19}{4}=0\end{matrix}\right.\) \(\Leftrightarrow...\)