\(\Leftrightarrow x\left(x^4-9\right)=0\Leftrightarrow x\left(x^2+3\right)\left(x-\sqrt{3}\right)\left(x+\sqrt{3}\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=0\\x^2+3=0\left(vô.nghiệm\right)\\x=\sqrt{3}\\x=-\sqrt{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\sqrt{3}\\x=-\sqrt{3}\end{matrix}\right.\)
\(x^5-9x=0\)
\(x\left(x^4-9\right)=0\)
\(x\left[\left(x^2\right)^2-3^2\right]=0\)
\(x\left(x^2+3\right)\left(x^2-3\right)=0\)
⇒\(\left[{}\begin{matrix}x=0\\x^2+3=0\\x^2-3=0\end{matrix}\right.\)
⇒\(\left[{}\begin{matrix}x=0\left(TM\right)\\x^2=-3\left(L\right)\\x^2=3\left(L\right)\end{matrix}\right.\)
\(x^5-9x=0\)
\(\Leftrightarrow x\left(x-\sqrt{3}\right)\left(x+\sqrt{3}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\sqrt{3}\\x=-\sqrt{3}\end{matrix}\right.\)
