\(\sqrt{x^2}+4x=2x+1\)
<=> \(|x|+4x=2x+1\)
<=> \(\left[{}\begin{matrix}x+4x=2x+1\\-x+4x=2x+1\end{matrix}\right.\)
<=> \(\left[{}\begin{matrix}x+4x-2x=1\\-x+4x-2x=1\end{matrix}\right.\)
<=> \(\left[{}\begin{matrix}3x=1\\x=1\end{matrix}\right.\)
<=> \(\left[{}\begin{matrix}x=\dfrac{1}{3}\\x=1\end{matrix}\right.\)