\[\boxed{\mathbf{635\ (635).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ x^{2} + mx - 6 = 0;\ \ \ \ x = 2\]
\[4 + 2m - 6 = 0\]
\[2m = 2\]
\[m = 1\]
\[Ответ:при\ m = 1.\]
\[2)\ 2x^{2} - 7x + m = 0;\ \ \ \ x = - 3\]
\[2 \cdot 9 + 21 + m = 0\]
\[m = 18 + 21\]
\[m = 39\]
\[Ответ:при\ m = 39.\]
\[3)\ m^{2}x^{2} + 14x - 3 = 0;\ \ \ \ x = \frac{1}{7}\]
\[\frac{m^{2}}{49} + 2 - 3 = 0\]
\[\frac{m^{2}}{49} = 1\]
\[m^{2} = 49\]
\[m = 7;\ \ m = - 7\]
\[Ответ:при\ m = \pm 7.\]