$\color{red}{1.}$
`x^3-4x=0`
`⇒x(x^2-4)=0`
`⇒x(x-2)(x+2)=0`
\(⇒\left[ \begin{array}{l}x=0\\x-2=0\\x+2=0\end{array} \right.\)
\(⇒\left[ \begin{array}{l}x=0\\x=2\\x=-2\end{array} \right.\)
Vậy `x=0; x=±2`
$\color{red}{2.}$
`x^2+xy-x-y`
`=(x^2+xy)-(x+y)`
`=x(x+y)-(x+y)`
`=(x+y)(x-1)`