ГДЗ по алгебре 7 класс Макарычев ФГОС Задание 886

\[\boxed{\text{886.}\text{\ }еуроки - ответы\ на\ пятёрку}\]

\[\textbf{а)}\ (0,8x + 15)(0,8x - 15) + 0,36x² = 0,64x² - 225 + 0,36x^{2} =\]

\[= x² - 225\]

\[\textbf{б)}\ 5b² + (3 - 2b)(3 + 2b) = 5b² + 9 - 4b^{2} = b^{2} + 9\]

\[\textbf{в)}\ 2x² - (x + 1)(x - 1) = 2x^{2} - \left( x^{2} - 1 \right) = 2x^{2} - x^{2} + 1 = x^{2} + 1\]

\[\textbf{г)}\ (3a - 1)(3a + 1) - 17a^{2} = 9a^{2} - 1 - 17a^{2} = - 8a^{2} - 1\]

\[\textbf{д)}\ 100x² - (5x - 4)(4 + 5x) =\]

\[= 100x^{2} - \left( 25x^{2} - 16 \right) = 100x^{2} - 25x^{2} + 16 = 75x^{2} + 16\]

\[\textbf{е)}\ 22c² + ( - 3c - 7)(3c - 7) = 22c² - (3c + 7)(3c - 7) =\]

\[= 22c² - \left( 9c^{2} - 49 \right) = 22c^{2} - 9c^{2} + 49 = 13c^{2} + 49\]