Lời giải:
a)
\(|2x+1|=|4x+7|\)
\(\Rightarrow \left[\begin{matrix} 2x+1=4x+7\\ 2x+1=-(4x+7)\end{matrix}\right.\)
\(\Rightarrow \left[\begin{matrix} 2x=-6\\ 6x=-8\end{matrix}\right.\Rightarrow \left[\begin{matrix} x=-3\\ x=-\frac{4}{3}\end{matrix}\right.\)
b) \(||2x-1|-8|=25\Rightarrow \left[\begin{matrix} |2x-1|-8=25\\ |2x-1|-8=-25\end{matrix}\right.\)
\(\Rightarrow \left[\begin{matrix} |2x-1|=33\\ |2x-1|=-17(\text{vô lý})\end{matrix}\right.\)
\(\Rightarrow \left[\begin{matrix} 2x-1=33\\ 2x-1=-33\end{matrix}\right.\Rightarrow \left[\begin{matrix} x=17\\ x=-16\end{matrix}\right.\)