2) y=-4/x
3) y=корень из x
4) y=-x/4
\[А\] | \[Б\] | \[В\] |
---|---|---|
\[3\] | \[4\] | \[1\] |
\[Всего:\ \ 100\%.\]
\[100\% - 88\% = 12\%.\]
\[Ответ:12\%.\]
\[4x(x + 3) = 4 - 3x\]
\[4x^{2} + 12x - 4 + 3x = 0\]
\[4x^{2} + 15x - 4 = 0\]
\[D = 225 + 64 = 289\]
\[x_{1} = \frac{- 15 + 17}{8} = \frac{2}{8} = \frac{1}{4} = 0,25;\]
\[x_{2} = \frac{- 15 - 17}{8} = - \frac{32}{8} = - 4.\]
\[Ответ:\ - 4;0,25.\]
\[\frac{b + 4}{b^{2} + 16} \cdot \left( \frac{b + 4^{\backslash b + 4}}{b - 4} + \frac{b - 4^{\backslash b - 4}}{b + 4} \right) =\]
\[= \frac{b + 4}{b^{2} + 16} \cdot \frac{b^{2} + 8b + 16 + b^{2} - 8b + 16}{(b - 4)(b + 4)} =\]
\[= \frac{1}{b^{2} + 16} \cdot \frac{2b^{2} + 32}{b - 4} = \frac{2 \cdot \left( b^{2} + 16 \right)}{\left( b^{2} + 16 \right)(b - 4)} =\]
\[= \frac{2}{b - 4}\]
\[b = 3,75:\]
\[\frac{2}{3,75 - 4} = \frac{2}{- 0,25} = - \frac{200}{25} = - 8.\]
\[Ответ:\ - 8.\]
\[Пусть\ \text{x\ }\frac{км}{ч} - скорость\ почтового\ \]
\[поезда;\]
\[(x + 10)\ \frac{км}{ч} - скорость\ скорого\ \]
\[поезда.\]
\[Составим\ уравнение:\]
\[\frac{180}{x} - \frac{160}{x + 10} = 2\ \ \ | \cdot x(x + 10)\]
\[180x + 1800 - 160x = 2x(x + 10)\]
\[20x + 1800 = 2x^{2} + 20x\]
\[2x^{2} + 20x - 20x - 1800 = 0\]
\[2x^{2} - 1800 = 0\]
\[2x^{2} = 1800\]
\[x^{2} = 900\]
\[x = - 30\ (не\ подходит).\]
\[x = 30\ \left( \frac{км}{ч} \right) - скорость\ почтового\ \]
\[поезда.\]
\[Ответ:\ 30\ \frac{км}{ч}.\]