Đáp án:
\(\left|2x+3\right|-4x< 9\)
\(\Leftrightarrow\left[{}\begin{matrix}2x+3-4x< 9\left(x>-\dfrac{3}{2}\right)\\-2x-3-4x< 9\left(x< -\dfrac{3}{2}\right)\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x>-3\\x>-2\end{matrix}\right.\Rightarrow x>-2\)
Vậy \(x>-2\) thì \(\left|2x+3\right|-4x< 9\)