ĐKXĐ: ...
\(\Leftrightarrow x^2+5x+4-\sqrt{x^2+5x+4}-2=0\)
Đặt \(\sqrt{x^2+5x+4}=a\ge0\)
\(a^2-a-2=0\Rightarrow\left[{}\begin{matrix}a=-1\left(l\right)\\a=2\end{matrix}\right.\)
\(\Rightarrow\sqrt{x^2+5x+4}=2\)
\(\Leftrightarrow x^2+5x=0\Rightarrow\left[{}\begin{matrix}x=0\\x=-5\end{matrix}\right.\)