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Question: Answered & Verified by Expert
If $\alpha, \beta, \gamma$ are the roots of $x^3+4 x+1=0$, then the equation whose roots are $\frac{\alpha^2}{\beta+\gamma}, \frac{\beta^2}{\gamma+\alpha}$, $\frac{\gamma^2}{\alpha+\beta}$ is
MathematicsQuadratic EquationAP EAMCETAP EAMCET 2009
Options:
  • A $x^3-4 x-1=0$
  • B $x^3-4 x+1=0$
  • C $x^3+4 x-1=0$
  • D $x^3+4 x+1=0$
Solution:
2897 Upvotes Verified Answer
The correct answer is: $x^3+4 x-1=0$
Given, $\alpha, \beta$ and $\gamma$ are the roots of
$\begin{aligned}
& x^3+4 x+1=0 . \\
& \begin{aligned}
& \therefore \alpha+\beta+\gamma=0, \alpha \beta+\beta \gamma+\gamma \alpha=4, \alpha \beta \gamma=-1 \\
& \text { Now, } \frac{\alpha^2}{\beta+\gamma}+\frac{\beta^2}{\gamma+\alpha}+\frac{\gamma^2}{\alpha+\beta}=\frac{\alpha^2}{-\alpha}+\frac{\beta^2}{-\beta}+\frac{\gamma^2}{-\gamma} \\
&=-(\alpha+\beta+\gamma)=0
\end{aligned} \\
& \frac{\alpha^2 \beta^2}{(\beta+\gamma)(\gamma+\alpha)}+\frac{\beta^2 \gamma^2}{(\gamma+\alpha)(\alpha+\beta)}+\frac{\gamma^2 \alpha^2}{(\beta+\gamma)(\alpha+\beta)}
\end{aligned}$
$\begin{aligned}=\alpha \beta+\beta \gamma+\gamma \alpha & =4 \\ \text { and } \quad \frac{\alpha^2 \beta^2 \gamma^2}{(\beta+\gamma)(\gamma+\alpha)(\alpha+\beta)} & =-\alpha \beta \gamma=1 \\ & (\because \alpha+\beta+\gamma=0)\end{aligned}$
$\therefore$ Required equation is
$x^3+4 x-1=0$

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