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AP EAMCET201825 Apr 2018Morning ShiftMathematicsSequences and SeriesActual

If 1 + 3 1 1 + 5 4 1 + 7 9 … 1 + 2 n + 1 n 2 = 121 , then n =

Options

  1. A11
  2. B9
  3. C10
  4. D8

Correct answer

C. 10

Step-by-step solution

Given: 1 + 3 1 1 + 5 4 1 + 7 9 … 1 + 2 n + 1 n 2 = 121 ⇒ 4 1 × 9 4 × 16 9 × . . . × n 2 + 2 n + 1 n 2 = 121 ⇒ n 2 + 2 n + 1 1 = 121 ⇒ n + 1 2 = 11 2 ⇒ n = 10 .

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