\[\boxed{\mathbf{454.ОК\ ГДЗ - домашка\ на}\ 5}\]
\[Рисунок\ по\ условию\ задачи:\]
\[\mathbf{Дано:}\]
\[{а)\ S}_{\text{ABCD}} = 250\ см^{2};\]
\[a = 2,5b.\]
\[{б)\ S}_{\text{ABCD}} = 9\ м^{2};\]
\[P_{\text{ABCD}} = 12\ м.\]
\[\mathbf{Найти:}\]
\[\mathbf{Решение.}\]
\[\textbf{а)}\ S_{\text{ABCD}} = 2,5b \bullet b = 2,5b^{2}\]
\[b^{2} = 100\ \]
\[b = 10\ см;\ \ \ \]
\[a = 2,5 \bullet 10 = 25\ см.\]
\[\textbf{б)}\ S_{\text{ABCD}} = \text{ab} = 9\ м^{2}.\]
\[P_{\text{ABCD}} = 2a + 2b = 12\ м:\]
\[a + b = 6\ \ \]
\[\ a = 6 - b.\]
\[S_{\text{ABCD}} = (6 - b)b = 9\]
\[6b - b^{2} = 9\]
\[b^{2} - 6b + 9 = 0\]
\[(b - 3)^{2} = 0\]
\[b = 3\ м;\ \ \]
\[\ a = 6 - 3 = 3\ м.\]
\[Ответ:а)\ a = 25\ см;b = 10\ см;\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ б)\ a = 3\ м;b = 3\ м.\]