Đk: \(x\ne k\pi\)
Ta có:
\(tanx+3cotx-4=0\\ \Leftrightarrow tannx+3\frac{1}{tanx}-4=0\\ \Leftrightarrow tan^2x-4tanx+3=0\\ \Leftrightarrow\left\{{}\begin{matrix}tanx=1\Rightarrow x=\frac{\pi}{4}+k\pi\\tanx=3\Rightarrow arctan3+k\pi\end{matrix}\right.\)