# Example 14 - Chapter 9 Class 11 Sequences and Series

Last updated at Jan. 11, 2019 by Teachoo

Last updated at Jan. 11, 2019 by Teachoo

Transcript

Example 14 The sum of first three terms of a G.P. is 13/12 and their product is โ 1. Find the common ratio and the terms. Let the three terms in G.P. be ๐/๐, a, ar here 1st term of G.P. = ๐/๐ 2nd term of G.P. = a 3rd term of G.P. = ar It is given that Sum of first three terms of G.P. = 13/12 i.e. a/r + a + ar = 13/12 (โ 1 โr โr2)/r = 13/12 12( -1 โ r โ r2 )= 13r -12 โ 12r โ 12r2 = 13r -12 - 12r - 12r2 โ 13r = 0 -12 - 25r - 12r2 = 0 -(12 + 25r + 12r2)= 0 12r2 + 25r + 12= 0 This equation is of the form ax2 + bx + c = 0 where a = 12 b = 25 c = 12 & x = r

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Chapter 9 Class 11 Sequences and Series

Serial order wise

About the Author

Davneet Singh

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.