|3x+4|=2|2x-9| giúp tôi giải bài này, không chép mạng

`|3x + 4| = 2 . |2x - 9|`

$\Leftrightarrow$ $\left[\begin{matrix} 3x+4=2.(2x-9)\\ 3x+4=2.[-(2x-9)]\end{matrix}\right.$

$\Leftrightarrow$ $\left[\begin{matrix} 3x+4=4x-18\\ 3x+4=2.(-2x+9)\end{matrix}\right.$

$\Leftrightarrow$ $\left[\begin{matrix} 3x-4x=-18-4\\ 3x+4=-4x+18\end{matrix}\right.$

$\Leftrightarrow$ $\left[\begin{matrix} -x=-22\\ 3x+4x=18-4\end{matrix}\right.$

$\Leftrightarrow$ $\left[\begin{matrix} x=22\\ 7x=14\end{matrix}\right.$

$\Leftrightarrow$ $\left[\begin{matrix} x=22\\ x=14:7\end{matrix}\right.$

$\Leftrightarrow$ $\left[\begin{matrix} x=22\\ x=2\end{matrix}\right.$

$\text{Vậy}$ `x \in {22 ; 2}`