\[3x^{2} + 2x = 0\]
\[3x\left( x + \frac{2}{3} \right) = 0\]
\[1)\ 3x = 0\]
\[x = 0.\]
\[2)\ x + \frac{2}{3} = 0\]
\[x = - \frac{2}{3}.\]
\[Ответ:x = - \frac{2}{3};x = 0.\]