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Question: Answered & Verified by Expert
If \( \alpha \) and \( \beta \) are the roots of \( x^{2}-a x+b^{2}=0 \), then \( \alpha^{2}+\beta^{2} \) is equal to
MathematicsDeterminantsKCETKCET 2015
Options:
  • A \( a^{2}-2 b^{2} \)
  • B \( 2 a^{2}-b^{2} \)
  • C \( a^{2}-b^{2} \)
  • D \( a^{2}+b^{2} \)
Solution:
1179 Upvotes Verified Answer
The correct answer is: \( a^{2}-2 b^{2} \)
Given equation,
$x^{2}-a x+b^{2}=0 \rightarrow(1)$
We know that, sum of the roots is given by
$\alpha+\beta=a$
and the product of the roots is given by
$\alpha \beta=b^{2}$
Now, $\alpha^{2}+\beta^{2}=(\alpha+\beta)^{2}-2 \alpha \beta$
$=a^{2}-2 b^{2}$

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