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

If 1+311+541+79…1+2n+1n2=121, then n=
  1. 11
  2. 9
  3. 10
  4. 8

Solution

Given:

1+311+541+79…1+2n+1n2=121

⇒41×94×169×...×n2+2n+1n2=121

⇒n2+2n+11=121

⇒n+12=112

⇒n=10.

Asked in: AP EAMCET 2018 (25 Apr Shift 1)

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