1. Chapter 8 Class 11 Sequences and Series
  2. Serial order wise
  3. Ex 8.2
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Ex 8.2, 11 - Chapter 8 Class 11 Sequences and Series

Last updated at Dec. 16, 2024 by Teachoo

Transcript

Ex9.3, 11 Introduction (2 + 3k) At k = 1, 2 + 31 At k = 2, 2 + 32 .. … …. At k = 11, 2 + 311 Ex9.3, 11 We calculate (31 + 32 + 33 + … + 311) separately In 31 + 32 + 33 + … + 311 32/31 = 3 & 33/32 = 3 Thus, (𝑆𝑒𝑐𝑜𝑛𝑑 𝑡𝑒𝑟𝑚)/(𝐹𝑖𝑟𝑠𝑡 𝑡𝑒𝑟𝑚) = (𝑇ℎ𝑖𝑟𝑑 𝑡𝑒𝑟𝑚)/(𝑆𝑒𝑐𝑜𝑛𝑑 𝑡𝑒𝑟𝑚) i.e. common ratio is same Thus, it is a G.P. First term = a = 3 Common ratio = 3^2/3^1 = 3 Since, r > 1 ∴ Sn = (𝑎(𝑟^𝑛 − 1))/(𝑟 − 1) where Sn = sum of n terms of GP n is the number of terms a is the first term & r is the common ratio ∴ Sn = (𝑎(𝑟^𝑛 − 1))/(𝑟 − 1) Putting values a = 3 , r = 3, n = 11 S11 = (3[311−1])/(3 − 1) S11 =(3[311−1])/2 Hence 31 + 32 + … + 311 = (3[311−1])/2 From (1) Putting 31 + 32 + … + 311 = (3[311−1])/2 = 22 + (3(311 − 1))/2 =22 + 3/2(311 −1) Therefore,
  1. Chapter 8 Class 11 Sequences and Series
  2. Serial order wise

    3. Ex 8.2

    Examples →
Examples →
Chapter 8 Class 11 Sequences and Series
Serial order wise

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Davneet Singh

Davneet Singh has done his B.Tech from Indian Institute of Technology, Kanpur. He has been teaching from the past 14 years. He provides courses for Maths, Science and Computer Science at Teachoo