Решебник по алгебре 9 класс Мерзляк Задание 420

\[\boxed{\text{420\ (420).\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[1)\ \sqrt{2x^{2} - 9x - 18}\]

\[2x^{2} - 9x - 18 \geq 0\]

\[D = 81 + 144 = 225\]

\[x_{1,2} = \frac{9 \pm 15}{4}\]

\[x = - 1,5;\ \ x = 6\]

\[Ответ:x \in ( - \infty; - 1,5\rbrack \cup \lbrack 6;\ + \infty).\]

\[2)\ \frac{1}{\sqrt{15 + 2x - x^{2}}}\]

\[15 + 2x - x^{2} > 0\]

\[- x^{2} + 2x + 15 > 0\]

\[x_{1} + x_{2} = 2,\ \ x_{1} = - 3\]

\[x_{1}x_{2} = - 15,\ \ x_{2} = 5\]

\[Ответ:x \in ( - 3;5).\]