`(x^2 - 10x + 21)(x^3 - x) = 0`
`<=>(x^2-3x-7x+21)(x^2-1)=0`
`<=>x(x-7)(x-3)(x^2-1)=0`
`<=>(x(x-7)(x-3)(x-1)(x+1)=0`
`⇔` \(\left[ \begin{array}{l}x=0\\x-7=0\\x-3=0\\x-1=0\\x+1=0\end{array} \right.\)
`⇔` \(\left[ \begin{array}{l}x=0\\x=7\\x=3\\x=1\\x=-1\end{array} \right.\)
`⇔ E = {0;7;3;1;-1}`
Xin hay nhất !