ГДЗ по алгебре 9 класс Макарычев Задание 647

\[\boxed{\text{647\ (646).}\text{\ }\text{Еуроки\ -\ ДЗ\ без\ мороки}}\]

\[\textbf{а)}\ 2x² - 13x - 34 \geq 0\]

\[2x^{2} - 13x - 34 = 0\]

\[D = 169 + 4 \cdot 2 \cdot 34 = 441\]

\[x_{1,2} = \frac{13 \pm 21}{4} = - 2;\ 8,5;\]

\[\Longrightarrow 2 \cdot (x + 2)(x - 8,5) \geq 0.\]

\[\]

\[x \in ( - \infty; - 2\rbrack \cup \lbrack 8,5; + \infty).\]

\[\textbf{б)}\ 10x - 4x^{2} < 0\]

\[4x^{2} - 10x > 0\]

\[x(2x - 5) > 0\]

\[x(x - 2,5) > 0\]

\[\]

\[x \in ( - \infty;0) \cup (2,5;\ + \infty).\]

\[\textbf{в)}\ \frac{x - 4}{2x + 5} \leq 0\]

\[(x - 4)(2x + 5) \leq 0,\ \ x \neq - 2,5\]

\[\]

\[x \in ( - 2,5;4\rbrack.\]