\[\boxed{\mathbf{627\ (627).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ x² + 7x = 0\]
\[x(x + 7) = 0\]
\[x = 0,\ \ x = - 7\]
\[Ответ:\ x = - 7;0.\]
\[2)\ 2x² - 11x = 0\]
\[x(2x - 11) = 0\]
\[x = 0,\ \ 2x - 11 = 0\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = 5,5\]
\[Ответ:x = 0;5,5.\]
\[3)\ 3x² - 6 = 0\]
\[3 \cdot \left( x^{2} - 2 \right) = 0\]
\[x^{2} - 2 = 0\]
\[x^{2} = 2\]
\[x = \sqrt{2},\ \ x = - \sqrt{2}\]
\[Ответ:\ x = - \sqrt{2};\sqrt{2}.\]
\[4) - 8x^{2} = 0\]
\[x^{2} = 0\]
\[x = 0\]
\[Ответ:x = 0.\]