a) $(2x+1)(x-1)=0$
$⇔ \left[ \begin{array}{l}2x+1=0\\x-1=0\end{array} \right.$
$⇔ \left[ \begin{array}{l}x=-\frac{1}{2}\\x=1\end{array} \right.$
b) $(x+\frac{2}{3})(x-\frac{1}{2})=0$
$⇔ \left[ \begin{array}{l}x+\frac{2}{3}=0\\x-\frac{1}{2}=0\end{array} \right.$
$⇔ \left[ \begin{array}{l}x=-\frac{2}{3}\\x=\frac{1}{2}\end{array} \right.$
c) $(3x-1)(2x-3)(x+5)=0$
$⇔ \left[ \begin{array}{l}3x-1=0\\2x-3=0\\x+5=0\end{array} \right.$
$⇔ \left[ \begin{array}{l}x=\frac{1}{3}\\x=\frac{3}{2}\\x=-5\end{array} \right.$
d) $3x-15=2x(x-5)$
$⇔3(x-5)-2x(x-5)=0$
$⇔(x-5)(3-2x)=0$
$⇔ \left[ \begin{array}{l}x-5=0\\3-2x=0\end{array} \right.$
$⇔ \left[ \begin{array}{l}3x=5\\x=\frac{3}{2}\end{array} \right.$
