ГДЗ по алгебре 8 класс Макарычев ФГОС Задание 840

\[\boxed{\text{840.\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]

\[(І)\ \ 3a(a + 6)\text{\ \ \ \ \ }и\text{\ \ \ }\]

\[\ (ІІ)\ (3a + 6)(a + 4)\text{\ \ \ }\]

\[при\ \ \ a = - 5:\ \ \ \ \]

\[3 \cdot ( - 5)( - 5 + 6) =\]

\[= - 15 \cdot 1 = - 15\]

\[\left( 3 \cdot ( - 5) + 6 \right)( - 5 + 4) =\]

\[= - 9 \cdot ( - 1) = 9\]

\[I < II.\]

\[при\ a = 0:\ \]

\[3 \cdot 0 \cdot (0 + 6) = 0\]

\[(3 \cdot 0 + 6)(0 + 4) = 6 \cdot 4 = 24\]

\[I < II.\]

\[при\ a = 40:\ \ \ \]

\[3 \cdot 40 \cdot (40 + 6) =\]

\[= 120 \cdot 46 = 5520\]

\[(3 \cdot 40 + 6)(40 + 4) =\]

\[= 126 \cdot 44 = 5544\]

\[I < II.\]

\[3a(a + 6) = 3a^{2} + 18a\]

\[(3a + 6)(a + 4) = 3a^{2} + 12a +\]

\[+ 6a + 24 = 3a² + 18a + 24\]

\[\Longrightarrow I < II \Longrightarrow ч.т.д.\]