ГДЗ по алгебре 9 класс Макарычев Задание 215

\[\boxed{\text{215}\text{\ (215)}\text{.}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

Пояснение.

Решение.

\[\textbf{а)}\ x = - 7;\ \ x = 2:\ \]

\[(x + 7)(x - 2) = x^{2} - 2x + 7x -\]

\[- 14 = x^{2} + 5x - 14;\]

\[\textbf{б)}\ x = 3 - \sqrt{2};\ \ x = 3 + \sqrt{2}:\]

\[\left( x - \left( 3 - \sqrt{2} \right) \right)\left( x - \left( 3 + \sqrt{2} \right) \right) =\]

\[= \left( x - 3 + \sqrt{2} \right)\left( x - 3 - \sqrt{2} \right) =\]

\[= \left( (x - 3) + \sqrt{2} \right) \cdot\]

\[\cdot \left( (x - 3) - \sqrt{2} \right) =\]

\[= (x - 3)^{2} - \left( \sqrt{2} \right)^{2} =\]

\[= x^{2} - 6x + 9 - 2 = x^{2} - 6x + 7.\]