`a`
`3(1-4x)(x-1)+4(3x+2)(x+3)=38`
`⇔3x-3-12x^2+12x^2+12x+8x+24+36x-38=0`
`⇔59x-17=0`
`⇔x=(17)/(59)`
`b`
`(8-5x)(x+2)+4(x-2)(x+1)+2(x-2)(x+2)=0`
`⇔8x-5x^2-16-10x+4x^2-8x+4x-8-8+2x^2=0`
`⇔x^2-4x=0`
`⇔x(x-4)=0`
`⇔`\(\left[ \begin{array}{l}x=0\\x=4\end{array} \right.\)