1.
\(\left|2x+1\right|+\left|x+8\right|=4x\)
Ta có: \(\left\{{}\begin{matrix}\left|2x+1\right|\ge0\\\left|x+8\right|\ge0\end{matrix}\right.\forall x.\)
Do đó, \(4x\ge0\Rightarrow x\ge0.\)
Lúc này ta có \(\left(2x+1\right)+\left(x+8\right)=4x\)
\(\Rightarrow\left(2x+x\right)+\left(1+8\right)=4x\)
\(\Rightarrow3x+9=4x\)
\(\Rightarrow4x-3x=9\)
\(\Rightarrow1x=9\)
\(\Rightarrow x=9:1\)
\(\Rightarrow x=9\left(TM\right).\)
Vậy \(x=9.\)
Chúc bạn học tốt!