ГДЗ по алгебре 8 класс Макарычев ФГОС Задание 841

\[\boxed{\text{841.\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]

\[(I)\ 4b \cdot (b + 1)\text{\ \ }\ \ \ и\text{\ \ \ \ \ \ \ }\]

\[(2b + 7)(2b - 8)\text{\ \ }\left( \text{II} \right)\]

\[при\ \ b = - 3:\ \ \]

\[4 \cdot ( - 3) \cdot ( - 3 + 1) =\]

\[= - 12 \cdot ( - 2) = 24\]

\[\left( 2 \cdot ( - 3) + 7 \right) \cdot \left( 2 \cdot ( - 3) - 8 \right) =\]

\[= 1 \cdot ( - 14) = - 14\]

\[I > II.\]

\[при\ b = - 2:\]

\[4 \cdot ( - 2) \cdot ( - 2 + 1) =\]

\[= - 8 \cdot ( - 1) = 8\]

\[\left( 2 \cdot ( - 2) + 7 \right)\left( 2 \cdot ( - 2) - 8 \right) =\]

\[= 3 \cdot ( - 12) = - 36\]

\[I > II.\]

\[при\ b = 10:\]

\[4 \cdot 10 \cdot (10 + 1) = 40 \cdot 11 = 440\]

\[(2 \cdot 10 + 7)(2 \cdot 10 - 8) =\]

\[= 27 \cdot 12 = 324\]

\[I > II.\]

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

\[(2b + 7)(2b - 8) = 4b^{2} -\]

\[- 16b + 14b - 56 =\]

\[= 4b^{2} - 2b - 56 =\]

\[= \left( 4b^{2} + 4b \right) - 6b -\]

\[- 56 \Longrightarrow I > II.\]