$\displaystyle \begin{array}{{>{\displaystyle}l}} \frac{3}{2x} -\frac{4x}{5} \geqslant 4\\ ĐK:\ x\neq 0\\ \Leftrightarrow \frac{15-8x^{2}}{10x} -4\geqslant 0\\ \Leftrightarrow \frac{15-8x^{2} -40x}{10x} \geqslant 0\\ Ta\ có\ bảng\ xét\ dấu\ như\ hình\ vẽ:\\ Vậy:x\in \left( -\infty ;\frac{-10-\sqrt{130}}{4}\right] \cup \left( 0;\frac{-10+\sqrt{130}}{4}\right] \end{array}$
