\(a,x^3-x=0\)
\(=x\left(x^2-1\right)=0\)
\(\Rightarrow\left\{{}\begin{matrix}x=0\\x^2-1=0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=0\\x= \pm {1}\end{matrix}\right.\)
Vậy \(x\in\left\{0,\sqrt{1}\right\}\)
\(b,x^2+x=0\)
\(=x\left(x+1\right)=0\)
\(\Rightarrow\left\{{}\begin{matrix}x=0\\x+1=0\end{matrix}\right.\Rightarrow\left\{{}\begin{matrix}x=0\\x=-1\end{matrix}\right.\)
Vậy \(x\in\left\{-1;0\right\}\)
