3x2-2x=0
=>x(3x-2)=0
=>x=0 hoặc x=2/3
3x2-2x=0
⇔ x( 3x-2)= 0
⇔\(\left[{}\begin{matrix}x=0\\3x-2=0\end{matrix}\right.\)
⇔\(\left[{}\begin{matrix}x=0\\3x=2\end{matrix}\right.\)
⇔\(\left[{}\begin{matrix}x=0\\x=\frac{2}{3}\end{matrix}\right.\)
S=\(\left\{0;\frac{2}{3}\right\}\)