Câu a :
\(5x\left(x-2018\right)-x+2018=0\)
\(5x\left(x-2018\right)-x+2018=0\)
\(\Leftrightarrow5x\left(x-2018\right)-\left(x-2018\right)=0\)
\(\Leftrightarrow\left(x-2018\right)\left(5x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-2018=0\\5x-1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2018\\x=\dfrac{1}{5}\end{matrix}\right.\)
Vậy \(x=\dfrac{1}{5}\) hoặc \(x=2018\)
Câu b :
\(x^3-2x=0\)
\(\Leftrightarrow x\left(x^2-2\right)=0\)
\(\Leftrightarrow x\left(x-\sqrt{2}\right)\left(x+\sqrt{2}\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x-\sqrt{2}=0\\x+\sqrt{2}=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\sqrt{2}\\x=-\sqrt{2}\end{matrix}\right.\)
Vậy \(x=-\sqrt{2}\) ; \(x=0\) hoặc \(x=\sqrt{2}\)
Wish you study well !!
