Решебник по алгебре 8 класс Мерзляк Задание 638

\[\boxed{\mathbf{638\ (638).\ }Еуроки\ - \ ДЗ\ без\ мороки}\]

\[1)\ x² - 4x + 3 = 0\]

\[x^{2} - 4x + 4 - 1 = 0\]

\[(x - 2)^{2} - 1 = 0\]

\[(x - 2 - 1)(x - 2 + 1) = 0\]

\[(x - 3)(x - 1) = 0\]

\[x = 3,\ \ x = 1.\]

\[Ответ:x = 1;x = 3.\]

\[2)\ x² + 6x - 7 = 0\]

\[x^{2} + 6x + 9 - 16 = 0\]

\[(x + 3)^{2} - 16 = 0\]

\[(x + 3 - 4)(x + 3 + 4) = 0\]

\[(x - 1)(x + 7) = 0\]

\[x = 1,\ \ x = - 7\]

\[Ответ:\ x = - 7;x = 1.\]

\[3)\ x² + 8x + 20 = 0\]

\[x^{2} + 8x + 16 + 4 = 0\]

\[(x + 4)^{2} = - 4\]

\[Ответ:нет\ корней.\]