\[\boxed{\text{519\ (}\text{с}\text{).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[1)\ x^{2} - 19 = 0\]
\[x^{2} = 19\]
\[x = \pm \sqrt{19}\]
\[2)\ x^{2} + 19 = 0\]
\[x^{2} = - 19\]
\[нет\ корней.\]
\[3)\ x^{2} - 19x = 0\]
\[x(x - 19) = 0\]
\[x = 0;\ \ \ \ \ \ \ x = 19.\]
\[4)\ x^{2} + 19x = 0\]
\[x(x + 19) = 0\]
\[x = 0;\ \ \ \ \ x = - 19.\]
\[Ответ:не\ имеет\ корней\ \]
\[уравнение\ №2.\ \]
\[\boxed{\text{519\ (}\text{н}\text{).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]
\[\textbf{а)}\ x^{2} - 19 = 0\]
\[x^{2} = 19\]
\[x = \pm \sqrt{19}\]
\[\textbf{б)}\ x^{2} + 19 = 0\]
\[x^{2} = - 19\]
\[нет\ корней.\]
\[\textbf{в)}\ x^{2} + 19x = 0\]
\[x(x + 19) = 0\]
\[x = 0;\ \ \ \ \ x = - 19.\]
\[Не\ имеет\ корней\ уравнение\ б),\ \]
\[так\ как\ x^{2}\ не\ может\ быть\ \]
\[отрицательным\ числом.\ \]
\[Ответ:б).\]