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JEE Mains · Maths · STD 11 - 8. sequence and series

यदि \(\sum_{r=1}^{25}\left(\frac{r}{r^{4}+r^{2}+1}\right)=\frac{p}{q}\) जहाँ p और q धनात्मक पूर्णांक हैं इस प्रकार कि gcd(p,q)=1, तो \(p+q\) = ___ है।

  1. A 976
  2. B 975
  3. C 977
  4. D 974
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Answer & Solution

Correct Answer

(A) 976

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Detailed explanation

\(S=\sum \frac{r}{\left(r^2+r+1\right)\left(r^2-r+1\right)}\) \(=\frac{1}{2} \sum_{ r =1}^{25}\left(\frac{1}{ r ^2- r +1}-\frac{1}{ r ^2+ r +1}\right)\)…
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