Решебник по алгебре 7 класс Мерзляк ФГОС Задание 816

\[\boxed{\text{816\ (816).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[a + c = 2b;\ \ \ a^{2} + 8bc =\]

\[= (2b + c)^{2}\]

\[a^{2} + 8\text{bc} = 4b^{2} + 4\text{bc} + c^{2}\]

\[a^{2} + 8\text{bc} - 4b^{2} - 4bc - c^{2} = 0\]

\[a^{2} + 4bc - 4b^{2} - c^{2} = 0\]

\[a^{2} = (c - 2b)^{2}\]

\[так\ как\ \ a + c = 2b \Longrightarrow \ \ a =\]

\[= 2b - c\]

\[(2b - c)^{2} = (c - 2b)^{2}\]

\[a^{2} = a^{2}.\]

\[\boxed{\text{816.\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[1)\ (1 - b^{2})\left( 1 + b^{2} + b^{4} \right) =\]

\[= 1 - b^{6}\]

\[при\ b = - 2:\ \ \]

\[1 - ( - 2)^{6} = 1 - 64 = - 63\]

\[2)\ 2x³ + 7 - (x + 1)\left( x^{2} - x + 1 \right) =\]

\[= 2x^{3} + 7 - x^{3} - 1 = x^{3} + 6\]

\[при\ x = - 1:\ \ \]

\[- 1 + 6 = 5\]