ГДЗ по алгебре 7 класс Макарычев Задание 769

\[\boxed{\text{769\ (769).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[\textbf{а)}\ (a - 3b)(a + 2b) + 5a(a + 2b) =\]

\[= (a + 2b)(a - 3b + 5a) =\]

\[= (a + 2b)(6a - 3b) =\]

\[= 3 \cdot (a + 2b)(2a - b)\]

\[\textbf{б)}\ (x + 8y)(2x - 5b) - 8y(2x - 5b) =\]

\[= (2x - 5b)(x + 8y - 8y) =\]

\[= x \cdot (2x - 5b)\]

\[\textbf{в)}\ 7a^{2}(a - x) + \left( 6a^{2} - ax \right)(x - a) =\]

\[= 7x^{2}(a - x) + \left( ax - 6a^{2} \right)(a - x) =\]

\[= (a - x)\left( 7a^{2} + ax - 6a^{2} \right) =\]

\[= (a - x)\left( a^{2} + ax \right) =\]

\[= a \cdot (a - x)(a + x)\]

\[= (3b - y)\left( 11b^{2} + 6y - 3b^{2} \right) =\]

\[= (3b - y)\left( 8b^{2} + 6y \right) =\]

\[= 2 \cdot (3b - y)(4b^{2} + 3y)\ \]