ГДЗ по алгебре 8 класс Макарычев ФГОС Задание 677

\[\boxed{\text{677\ (677).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[5x^{2} - 12x + c = 0,\ \ x_{1} = 3x_{2}\]

\[x^{2} - \frac{12}{5}x + \frac{c}{5} = 0\]

\[c = 15 \cdot \left( \frac{3}{5} \right)^{2} = 15 \cdot \frac{9}{25} =\]

\[= 3 \cdot 9\ :5 = \frac{27}{5} = 5,4.\]

\[Ответ:c = 5,4.\ \]

\[\boxed{\text{677.}\text{\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]

\[\textbf{а)}\ 3x - 2y = 5\]

\[2y = 3x - 5\]

\[y = 1,5x - 2,5.\]

\[\textbf{б)}\ x + 2y - 3 = 0\]

\[2y = 3 - x\]

\[y = 1,5 - 0,5x.\]

\[\textbf{в)}\ 3x - 4y = - 1\]

\[4y = 3x + 1\]

\[y = \frac{3}{4}x + \frac{1}{4}.\]