Question

(x²-3x).(x²-9) =0

Answer 1

\(\left(x^2-3x\right)\left(x^2-9\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x^2-3x=0\\x^2-9=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x\left(x-3\right)=0\\\left(x-3\right)\left(x+3\right)=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}\left[{}\begin{matrix}x=0\\x=3\end{matrix}\right.\\\left[{}\begin{matrix}x=3\\x=-3\end{matrix}\right.\end{matrix}\right.\)

Vậy : Phương trình có tập nghiệm \(S=\left\{-3;0;3\right\}\)