\[\boxed{\mathbf{550.ОК\ ГДЗ - домашка\ на}\ 5}\]
\[\textbf{а)}\ Рисунок\ по\ условию\ задачи:\]
\[Дано:\ \]
\[\mathrm{\Delta}ABC;\ \mathrm{\Delta}CDE;\]
\[AB = 8;\]
\[AC = 12;\]
\[CD = 6;\]
\[ED = x;\ \]
\[\angle BCA = \angle E.\]
\[Найти:\]
\[ED - ?\]
\[Решение:\]
\[\frac{\text{AB}}{\text{DC}} = \frac{\text{BC}}{\text{CE}} = \frac{\text{AC}}{\text{DC}}\]
\[\frac{8}{6} = \frac{12}{x}\]
\[x = 9 \Longrightarrow ED = 9.\]
\[Ответ:ED = 9.\]
\[\textbf{б)}\ Рисунок\ по\ условию\ задачи:\]
\[Дано:\ \]
\[\mathrm{\Delta}ABC;\ \mathrm{\Delta}CDE;\]
\[AD = 20;\]
\[DC = 8;\]
\[EC = 10;\]
\[BA = y;\ \]
\[\angle A = \angle D = 90{^\circ}.\]
\[Найти:\]
\[BA - ?\]
\[Решение:\]
\[\frac{\text{AB}}{\text{DE}} = \frac{\text{AC}}{\text{DC}} = \frac{\text{BC}}{\text{EC}}.\]
\[2)\ DE = \sqrt{100 - 64} = 6;\]
\[\frac{\text{AB}}{6} = \frac{28}{8}\]
\[AB = 21.\]
\[Ответ:BA = 21.\]
\[\boxed{\mathbf{550.еуроки - ответы\ на\ пятёрку}}\]
\[Рисунок\ по\ условию\ задачи:\]
\[\mathbf{Дано:}\]
\[{а)\ S}_{\text{ABCD}} = 250\ см^{2};\]
\[a = 2,5\text{b.}\]
\[{б)\ S}_{\text{ABCD}} = 9\ м^{2};\]
\[P_{\text{ABCD}} = 12\ м.\]
\[\mathbf{Найти:}\]
\[\mathbf{Решение.}\]
\[\textbf{а)}\ S_{\text{ABCD}} = 2,5b \bullet b = 2,5b^{2}\]
\[b^{2} = 100\ \]
\[b = 10\ см;\ \ \ \]
\[a = 2,5 \bullet 10 = 25\ см.\]
\[\textbf{б)}\ S_{\text{ABCD}} = ab = 9\ м^{2}.\]
\[P_{\text{ABCD}} = 2a + 2b = 12\ м:\]
\[a + b = 6\ \ \]
\[\ a = 6 - b.\]
\[S_{\text{ABCD}} = (6 - b)b = 9\]
\[6b - b^{2} = 9\]
\[b^{2} - 6b + 9 = 0\]
\[(b - 3)^{2} = 0\]
\[b = 3\ м;\ \ \]
\[\ a = 6 - 3 = 3\ м.\]
\[Ответ:а)\ a = 25\ см;b = 10\ см;\]
\[\ \ \ \ \ \ \ \ \ \ \ \ \ \ б)\ a = 3\ м;b = 3\ м.\]