Решебник по алгебре 7 класс Мерзляк Задание 449

\[\boxed{\text{449\ (449).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[5 \cdot (x + 7) = 0\]

\[x + 7 = 0\]

\[x = - 7.\]

\[Ответ:\ x = - 7.\]

\[(x - 2) \cdot (4x - 9 + 1 - x) = 0\]

\[(x - 2) \cdot (3x - 8) = 0\]

\[x - 2 = 0\ \ или\ \ 3x - 8 = 0\]

\[Ответ:x = 2;2\frac{2}{3}.\]

\[3)\ 0,2x \cdot (x - 5) + 8 \cdot (x - 5) =\]

\[= 0\]

\[(x - 5) \cdot (0,2x + 8) = 0\]

\[x - 5 = 0\ \ или\ \ 0,2x + 8 = 0\]

\[\ \ \ \ \ \ \ \ x = 5\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = - 40.\]

\[Ответ:x = 5;\ - 40.\]

\[4)\ 7 \cdot (x - 7) - (x - 7)^{2} = 0\]

\[7 \cdot (x - 7) - (x - 7)(x - 7) = 0\]

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

\[(x - 7) \cdot (14 - x) = 0\]

\[x - 7 = 0\ \ или\ \ 14 - x = 0\]

\[\ \ \ \ \ \ \ \ x = 7\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ x = 14.\]

\[Ответ:x = 7;14.\ \]