Mathematics › Quadratic Equation › Relation between Roots and Coefficients
If the roots of $\sqrt{\frac{1-y}{y}}+\sqrt{\frac{y}{1-y}}=\frac{5}{2}$ are $\alpha$ and…
If the roots of $\sqrt{\frac{1-y}{y}}+\sqrt{\frac{y}{1-y}}=\frac{5}{2}$ are $\alpha$ and $\beta(\beta\gt\alpha)$ and the equation $(\alpha+\beta) x^4-25 \alpha \beta x^2+(\gamma+\beta-\alpha)=0$ has real roots, then a possible value of $\gamma$ is
$\frac{1}{2}$ 4 $2 \pi$ $\sqrt{e+13}$
Solution
$\sqrt{\frac{1-y}{y}}+\sqrt{\frac{y}{1-y}}=\frac{5}{2}$
$\begin{aligned} & \frac{1}{\sqrt{y(1-y)}}=\frac{5}{2} \Rightarrow y(1-y)=\frac{4}{25} \\ & 25 y(1-y)=4 \Rightarrow 25 y^2-25 y+4=0 \\ & \alpha+\beta=1 \\ & \alpha \beta=\frac{4}{25} \\ & \beta-\alpha=\sqrt{1-\frac{16}{25}}=\frac{3}{5} \\ & x^4-4 x^2+\left(\frac{3}{5}+\gamma\right)=0 \\ & x^2=\frac{4 \pm \sqrt{16-4\left(\frac{3}{5}+\gamma\right)}}{2}=\frac{4 \pm 2 \sqrt{\frac{17}{5}-\gamma}}{2}\end{aligned}$
$\begin{aligned} & \therefore 2+\sqrt{\frac{17}{5}-\gamma}\gt0 \forall \gamma \in \mathrm{R} \\ & 2-\sqrt{\frac{17}{5}-\gamma\gt0} \Rightarrow 2\gt\sqrt{\frac{17}{5}-\gamma} \\ & 4\gt\frac{17}{5}-\gamma \Rightarrow \gamma\gt-\frac{3}{5} \Rightarrow \frac{17}{5}-\gamma\gt0 \Rightarrow \gamma \lt \frac{17}{5} \\ & \gamma \in\left(\frac{-3}{5}, \frac{17}{5}\right)\end{aligned}$
Asked in: AP EAMCET 2024 (20 May Shift 2)
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