Example 9 - Chapter 8 Class 11 Sequences and Series
Last updated at Dec. 16, 2024 by Teachoo
Last updated at Dec. 16, 2024 by Teachoo
Example 9 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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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