Решебник по алгебре 8 класс Мерзляк ФГОС Задание 729

\[\boxed{\mathbf{729\ (729).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]

\[1)\ 2x² - 5x + 3 = 0\]

\[x_{1} + x_{2} = \frac{5}{2},\ \ x_{1} = 1\]

\[x_{1} \cdot x_{2} = \frac{3}{2},\ \ x_{2} = \frac{3}{2} = 1,5\]

\[Ответ:x = 1;x = 1,5.\]

\[2)\ 2x² + 5x + 3 = 0\]

\[x_{1} + x_{2} = - \frac{5}{2},\ \ x_{1} = - 1\]

\[x_{1} \cdot x_{2} = \frac{3}{2},\ \ x_{2} = - \frac{3}{2} = - 1,5\]

\[Ответ:\ x = - 1;\ x = - 1,5.\]

\[3)16x² - 23x + 7 = 0\]

\[x_{1} + x_{2} = \frac{23}{16},\ \ x_{1} = \frac{7}{16}\]

\[x_{1} \cdot x_{2} = \frac{7}{16},\ \ x_{2} = 1\]

\[Ответ:x = \frac{7}{16};x = 1.\]

\[4) - 8x^{2} - 19x + 27 = 0\]

\[x_{1} + x_{2} = - \frac{19}{8},\ \ \]

\[x_{1} = - \frac{27}{8} = - 3\frac{3}{8}\]

\[x_{1} \cdot x_{2} = - \frac{27}{8},\ \ x_{2} = 1\]

\[Ответ:\ x = - 3\frac{3}{8};x = 1.\]

\[\boxed{\mathbf{72}\mathbf{9}\mathbf{\text{.\ }}Еуроки\ - \ ДЗ\ без\ мороки}\]

\[x^{2} + bx - 7 = 0\]

\[D = b^{2} + 28 > 0,\ \ \]

\[при\ \ любом\ b.\]