Xét đa thức \(3x^3+x^2=0\)
\(\Rightarrow x^2\left(3x+1\right)=0\)
\(\Rightarrow\left[{}\begin{matrix}x^2=0\\3x+1=0\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\3x=-1\end{matrix}\right.\)
\(\Rightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{1}{3}\end{matrix}\right.\)
Vậy ....