ĐKXĐ; ...
\(\Leftrightarrow\left(x^2-8x+16\right)+\left(3x+4-8\sqrt{3x+4}+16\right)=0\)
\(\Leftrightarrow\left(x-4\right)^2+\left(\sqrt{3x+4}-4\right)^2=0\)
\(\Leftrightarrow\left\{{}\begin{matrix}x-4=0\\\sqrt{3x+4}-4=0\end{matrix}\right.\)
\(\Leftrightarrow x=4\)