`4x^2-x=0`
`<=>x(4x-1)=0`
`<=>`\(\left[ \begin{array}{l}x=0\\4x-1=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=0\\x=\dfrac{1}{4}\end{array} \right.\)
Vậy `S={0;1/4}`
`x-3x^2=0`
`<=>x(1-3x)=0`
`<=>`\(\left[ \begin{array}{l}x=0\\1-3x=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=0\\x=\dfrac{1}{3}\end{array} \right.\)
Vậy `S={0;1/3}`
`4x^2-36=0`
`<=>(2x-6)(2x+6)=0`
`<=>`\(\left[ \begin{array}{l}2x-6=0\\2x+6=0\end{array} \right.\)
`<=>`\(\left[ \begin{array}{l}x=3\\x=-3\end{array} \right.\)
Vậy `S={±3}`
