\(\begin{array}{*{20}{l}}{a)\,5x\left( {x - 2000} \right) - x + 2000 = 0}\\{5x\left( {x - 2000} \right) - \left( {x - 2000} \right) = 0}\\\begin{array}{l}\left( {x - 2000} \right)\left( {5x - 1} \right) = 0\\ \Rightarrow \left[ \begin{array}{l}x - 2000 = 0\\5{\rm{x}} - 1 = 0\end{array} \right. \Rightarrow \left[ \begin{array}{l}x = 2000\\x = \dfrac{1}{5}\end{array} \right.\end{array}\end{array}\)
Vậy \(x = \dfrac{1}{5}\) hoặc \(x = 2000\)
\(\begin{array}{*{20}{l}}{b)\,{\rm{ }}{x^3}-13x = 0}\\x.x^2-13x=0\\\begin{array}{l}x\left( {{x^2} - {\rm{ 1}}3} \right) = 0\\ \Rightarrow \left[ \begin{array}{l}x = 0\\{x^2} - 13 = 0\end{array} \right. \Rightarrow \left[ \begin{array}{l}x = 0\\x = \pm \sqrt {13} \end{array} \right.\end{array}\end{array}\)
Vậy \( x = 0\) hoặc \(x = \pm \sqrt {13} \)
