Решебник по алгебре 8 класс Мерзляк ФГОС Задание 708

\[\boxed{\mathbf{708\ (708).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]

\[1)\ x² - 12x - 18 = 0\]

\[x_{1} + x_{2} = 12\]

\[x_{1}x_{2} = - 18\]

\[2)\ x² + 2x - 9 = 0\]

\[x_{1} + x_{2} = - 2\]

\[x_{1}x_{2} = - 9\]

\[3)\ 3x² + 7x + 2 = 0\]

\[x_{1} + x_{2} = - \frac{7}{3}\]

\[x_{1}x_{2} = \frac{2}{3}\]

\[4) - 4x^{2} - 8x + 27 = 0\]

\[x_{1} + x_{2} = \frac{8}{- 4} = - 2\]

\[x_{1}x_{2} = - \frac{27}{4} = - 6,75\]

\[\boxed{\mathbf{708.\ }Еуроки\ - \ ДЗ\ без\ мороки}\]

\[x^{2} - 0,5ax - 3a^{2} = 0;\ \ x = 2\]

\[4 - a - 3a^{2} = 0\]

\[3a^{2} + a - 4 = 0\]

\[D = 1 + 48 = 49\]

\[a = \frac{- 1 \pm \sqrt{49}}{6} = \frac{- 1 \pm 7}{6}\]

\[a_{1} = 1\]

\[a_{2} = - \frac{4}{3} = - 1\frac{1}{3}\]

\[Ответ:при\ a = 1;\ a = - 1\frac{1}{3}.\]