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If the equation \(x^{2}-c x+d=0\) has roots equal to the fourth powers of the roots of \(x^{2}+a x+b=0\), where \(a^{2}>4 b\), then the roots of \(x^{2}-4 b x+2 b^{2}-c=0\) will be
(A) both real
(B) both negative
(C) both positive
(D) one positive and one negative

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Ans: (A, D)
Hint : \(x^{2}-4 b x+2 b^{2}-c=0\)
let \(\alpha_{1}, \beta_{1}\) be roots
$$
\begin{aligned}
\alpha_{1}, \beta_{1} &=2 b^{2}-c \\
&=2 b^{2}-\left(a^{4}-4 a^{2} b+2 b^{2}\right) \\
&=a^{2}\left(4 b-a^{2}\right)<0
\end{aligned}
$$
Hence one positive and one negative
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