ĐKXĐ: ...
\(\Leftrightarrow\left(\frac{x^2}{x+1}\right)^2+\frac{x^2}{x+1}-12=0\)
Đặt \(\frac{x^2}{x+1}=t\)
\(\Rightarrow t^2+t-12=0\Rightarrow\left[{}\begin{matrix}t=3\\t=-4\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}\frac{x^2}{x+1}=3\\\frac{x^2}{x+1}=-4\end{matrix}\right.\) \(\Leftrightarrow\left[{}\begin{matrix}x^2-3x-3=0\\x^2+4x+4=0\end{matrix}\right.\) \(\Rightarrow\) bấm casio