Решебник по алгебре 7 класс Макарычев ФГОС Задание 697

 

\[\boxed{\text{697.}\text{\ }еуроки - ответы\ на\ пятёрку}\]

Пояснение.

Решение.

\[\textbf{а)}\ \left( 2x^{2} - y \right)\left( x^{2} + y \right) =\]

\[= 2x^{4} + 2x^{2}y - yx^{2} - y^{2} =\]

\[= 2x^{4} + x^{2}y - y²\]

\[\textbf{б)}\ \left( 7x^{2} + a^{2} \right)\left( x^{2} - 3a^{2} \right) =\]

\[= 7x^{4} - 21a^{2}x^{2} + a^{2}x^{2} - 3a^{4} =\]

\[= 7x^{4} - 20a^{2}x^{2} - 3a^{4}\]

\[\textbf{в)}\ \left( 11y^{2} - 9 \right)(3y - 2) =\]

\[= 33y³ - 22y^{2} - 27y + 18\]

\[\textbf{г)}\ \left( 5a - 3a^{3} \right)(4a - 1) =\]

\[= 20a² - 5a - 12a^{4} + 3a³\ \]

\[\boxed{\text{697\ (697).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[\textbf{а)}\ (3x - 1)(5x + 4) - 15x^{2} = 17\]

\[15x^{2} + 12x - 5x - 4 - 15x^{2} =\]

\[= 17\]

\[7x = 17 + 4\]

\[7x = 21\]

\[x = 3\]

\[Ответ:x = 3.\]

\[\textbf{б)}\ (1 - 2x)(1 - 3x) =\]

\[= (6x - 1)x - 1\]

\[1 - 3x - 2x + 6x^{2} = 6x^{2} - x - 1\]

\[1 - 5x + 6x^{2} - 6x^{2} + x = - 1\]

\[- 4x = - 1 - 1\]

\[- 4x = - 2\]

\[x = 0,5\]

\[Ответ:x = 0,5.\]

\[\textbf{в)}\ 12 - x(x - 3) =\]

\[= (6 - x)(x + 2)\]

\[12 - x^{2} + 3x =\]

\[= 6x + 12 - x^{2} - 2x\]

\[- x = 0\]

\[x = 0\]

\[Ответ:x = 0.\]

\[\textbf{г)}\ (x + 4)(x + 1) =\]

\[= x - (x - 2)(2 - x)\]

\[x^{2} + x + 4x + 4 =\]

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

\[8x = 0\]

\[x = 0\]

\[Ответ:x = 0.\]