`a)5x(x-2000)-x+2000=0`
`<=>5x(x-2000)-(x-2000)=0`
`<=>(x-2000)(5x-1)=0`
`<=>` \(\left[ \begin{array}{l}x-200=0\\5x-1=0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=2000\\x=\dfrac{1}{5}\end{array} \right.\)
Vậy `x=2000; x=1/5`
`b) x^3-13x=0`
`<=> x(x^2-13)=0`
`<=>` \(\left[ \begin{array}{l}x=0\\x^2-13=0\end{array} \right.\)
`<=>` \(\left[ \begin{array}{l}x=0\\x^2=13\end{array} \right.\) \(\left[ \begin{array}{l}x=0\\\left[\begin{matrix} x=\sqrt{13}\\ x=\sqrt{-13}\end{matrix}\right.\end{array} \right.\)
Vậy `x=0;x=\sqrt{13}; \sqrt{-13}`
