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  1. Class 11
  2. Important Question for exams Class 11

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‘Ž/๐‘Ÿ, a, ar here 1st term of G.P. = ๐‘Ž/๐‘Ÿ 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 (โˆ’ 1 โˆ’r โˆ’r2)/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

About the Author

Davneet Singh's photo - Teacher, Computer Engineer, Marketer
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.