1. Chapter 9 Class 11 Sequences and Series
  2. Serial order wise
  3. Miscellaneous

Misc 22 - Chapter 9 Class 11 Sequences and Series

Last updated at May 29, 2018 by

Misc 22 - Find 20th term of series 2 x 4 + 4 x 6 + 6 x 8 - Finding sum from nth number

  1. Chapter 9 Class 11 Sequences and Series
  2. Serial order wise

    3. Miscellaneous

    Concept wise →

Transcript

Misc 22 Find the 20th term of the series 2 × 4 + 4 × 6 + 6 × 8 + … + n terms. Now, an = [nth term of 2, 4, 6 …] × [nth term of 4, 6, 8 …] = (2n) (2n + 2) = (2n) (2(n + 1)) = 4n (n + 1) Thus, nth term of series 2 × 4 + 4 × 6 + 6 × 8… is an = 4n (n + 1) We need to find 20th term of given series Putting n = 20 a20 = 4 × 2(20 + 1) = 80 (21) = 1680 Hence 20th term of series is 1680

Chapter 9 Class 11 Sequences and Series
Serial order wise

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Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 9 years. He provides courses for Maths and Science at Teachoo.