`a,3x(x-4)+12x-48=0`
`⇔3x(x-4)+12(x-4)=0`
`⇔(x-4)(3x+12)=0`
`⇔(x-4)3(x+4)=0`
`⇔(x-4)(x+4)=0`
`⇔` \(\left[ \begin{array}{l}x-4=0\\x+4=0\end{array} \right.\) `⇔` \(\left[ \begin{array}{l}x=4\\x=-4\end{array} \right.\)
`b,x^2(x-2)=x-2`
`⇔x^2(x-2)-(x-2)=0`
`⇔(x^2-1)(x-2)=0`
`⇔` \(\left[ \begin{array}{l}x^2-1=0\\x-2=0\end{array} \right.\) `⇔` \(\left[ \begin{array}{l}x=±1\\x=2\end{array} \right.\)