Решебник по алгебре 9 класс Мерзляк Задание 201

\[\boxed{\text{201\ (201).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[1)\ \left\{ \begin{matrix} - x < 2 \\ 2x > 7 \\ x < - 4 \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ }\left\{ \begin{matrix} x > - 2 \\ x > 3,5 \\ x < - 4 \\ \end{matrix} \right.\ \ \]

\[Ответ:\ \varnothing.\ \]

\[2)\ \left\{ \begin{matrix} 3x - 1 < 2x + 2 \\ 2x + 1 > 8 - 5x \\ 5x - 25 \leq 0\ \ \ \ \ \ \ \ \\ \end{matrix} \right.\ \text{\ \ \ \ \ \ \ \ \ \ \ }\]

\[\left\{ \begin{matrix} x < 3\ \ \ \ \\ 7x > 7\ \ \\ 5x \leq 25 \\ \end{matrix}\text{\ \ } \right.\ \text{\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ }\left\{ \begin{matrix} x < 3 \\ x > 1 \\ x \leq 5 \\ \end{matrix} \right.\ \]

\[Ответ:x \in (1;3)\text{.\ }\]

\[\boxed{\text{201.\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[\left\{ \begin{matrix} a \cdot b = 2400 \\ a + b = 110 \\ \end{matrix} \right.\ \]

\[\left\{ \begin{matrix} a = (110 - b)\text{\ \ \ \ \ \ \ \ \ \ } \\ (110 - b)b = 2400 \\ \end{matrix} \right.\ \]

\[110b - b^{2} = 2400\]

\[b^{2} - 110b + 2400 = 0\]

\[D_{1} = 3025 - 2400 = 625\]

\[b_{1} = 55 - 25 = 30\ (м);\]

\[b_{2} = 55 + 25 = 80\ (м).\]

\[a_{1} = 110 - b = 110 - 30 = 80\ м;\]

\[a_{2} = 110 - b = 110 - 80 = 30\ м.\]

\[Ответ:30\ м\ и\ 80\ м.\]