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BITSAT2012MathematicsSequences and SeriesActual

Let a₁, a₂, a₃ . be terms on A.P. If a₁+a₂+ a_ p a₁+a₂+ .+a_ q = p² q² , p q, then a₆ a₂₁ equals

Options

  1. A41 11
  2. B7 2
  3. C2 7
  4. D11 41

Correct answer

D. 11 41

Step-by-step solution

p 2 [2 a₁+(p-1) d ] q 2 [2 a₁+(q-1) d ] = p² q² 2 a₁+(p-1) d 2 a₁+(q-1) d = p q a₁+ ( p-1 2 ) d a₁+ ( q-1 2 ) d = p q For a₆ a₂₁ , p=11, q=41

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