ГДЗ по алгебре 7 класс Макарычев ФГОС Задание 891

\[\boxed{\text{891.}\text{\ }еуроки - ответы\ на\ пятёрку}\]

\[\textbf{а)}\ 5a(a - 8) - 3 \cdot (a + 2)(a - 2) = 5a^{2} - 40a - 3 \cdot \left( a^{2} - 4 \right) =\]

\[= 5a² - 40a - 3a^{2} + 12 = 2a^{2} - 40a + 12\]

\[\textbf{б)}\ (1 - 4b)(4b + 1) + 6b \cdot (b - 2) = 1 - 16b^{2} + 6b^{2} - 12b =\]

\[= - 10b^{2} - 12b + 1\]

\[\textbf{в)}\ (8p - q)(q + 8p) - (p + q)(p - q) = 64p^{2} - q^{2} - \left( p^{2} - q^{2} \right) =\]

\[= 64p² - q^{2} - p^{2} + q^{2} = 63p²\]

\[\textbf{г)}\ (2x - 7y)(2x + 7y) + (2x - 7y)(7y - 2x) = 4x² - 49y^{2} - (7y - 2x)^{2} =\]

\[= 4x^{2} - 49y^{2} - \left( 49y^{2} - 28xy + 4x^{2} \right) = 4x^{2} - 49y^{2} - 49y^{2} + 28xy - 4x^{2} =\]

\[= - 98y^{2} + 28xy\]