\(x^3+2x^2+x=0\)
\(\Leftrightarrow x\left(x^2+2x+1\right)=0\)
\(\Leftrightarrow x\left(x+1\right)^2=0\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x+1=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=-1\end{matrix}\right.\)
\(x^3+2x^2+x=0\\ =>x\left(x^2+2x+1\right)=0\\ =>x\left(x+1\right)^2=0\\ =>\left[{}\begin{matrix}x=0\\\left(x+1\right)^2=0\end{matrix}\right.=>\left[{}\begin{matrix}x=0\\x+1=0\end{matrix}\right.=>\left[{}\begin{matrix}x=0\\x=-1\end{matrix}\right.\)
\(x^3+2x^2+x=0\)
\(x\left(x^2+2x+1\right)=0\)
\(x\left(x+1\right)^2=0\)
\(\Rightarrow\left\{{}\begin{matrix}x=0\\\left(x+1\right)^2=0\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}x=0\\x+1=0\end{matrix}\right.\)
\(\Rightarrow\left\{{}\begin{matrix}x=0\\x=0-1=-1\end{matrix}\right.\)
\(\text{Vậy x}\in\left\{0;-1\right\}\)
