a) [tex]\frac{\left(x-4\right)\left(2x+1\right)}{1-x}=0\\\left(x-4\right)\left(2x+1\right)=0\\\boxed{x=4,\:x=-\frac{1}{2}\\}[/tex]
b) [tex]\frac{\left(x+1\right)}{\left(x+2\right)}-\frac{\left(x+2\right)}{\left(x-3\right)}=0\\-6x-7=0\\-6x-7+7=0+7\\\frac{-6x}{-6}=\frac{7}{-6}\\x=-\frac{7}{6}\\\boxed{x=-1\frac{1}{6}}[/tex]
