$a)(2x-4)(3x+15)\le0$
$\Leftrightarrow\begin{cases} 2x-4\ge0\\3x+15\le0 \end{cases}$
$\Leftrightarrow\begin{cases} 2x\le4\\3x\ge-15 \end{cases}$
$\Leftrightarrow\begin{cases} x\le2\\x\ge-5 \end{cases}$
$\Leftrightarrow-5<x<2$
Vậy $-5<x<2$
$b)\dfrac{4x-1}{2}>\dfrac{-3x+1}{3}$
$\Leftrightarrow\dfrac{3(4x-1)}{6}>\dfrac{2(-3x+1)}{6}$
$\Leftrightarrow\dfrac{12x-3}{6}>\dfrac{-6x+2}{6}$
$\Rightarrow12x-3>-6x+2$
$\Leftrightarrow18x>5$
$\Leftrightarrow x>\dfrac{5}{18}$
Vậy $x>\dfrac{5}{18}$
