ГДЗ по алгебре 8 класс Макарычев ФГОС Задание 518

\(\boxed{\text{518.}\text{\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\)

\[\textbf{а)}\ 5a^{2} + 5a - 6 = 24\]

\[5a^{2} + 5a - 30 = 0\ \ \ |\ :5\]

\[a^{2} + a - 6 = 0\]

\[D = 1 + 24 = 25\]

\[a_{1} = \frac{- 1 + 5}{2} = 2;\ \ \]

\[a_{2} = \frac{- 1 - 5}{2} = - 3.\]

\[Ответ:при\ \ a = - 3;\ \ a = 2.\]

\[\textbf{б)}\ \ a(a - 4) = 60\]

\[a^{2} - 4a - 60 = 0\]

\[D_{1} = 4 + 60 = 64\]

\[a_{1} = 2 + 8 = 10;\ \ \]

\[a_{2} = 2 - 8 = - 6.\]

\[Ответ:при\ a = - 6;a = 10.\]