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Example 14 - Chapter 9 Class 11 Sequences and Series (Term 1)
Last updated at Jan. 11, 2019 by Teachoo
Examples
Example 1 (i)
Example 1 (ii)
Example 2
Example 3 Important
Example 4
Example 5
Example 6 Important
Example 7
Example 8 Important
Example 9
Example 10 Important
Example 11
Example 12 Important
Example 13
Example 14 Important You are here
Example 15 Important
Example 16
Example 17 Important
Example 18 Important
Example 19 Important
Example 20
Example 21 Important
Example 22
Example 23
Example 24 Important
Chapter 9 Class 11 Sequences and Series
Serial order wise
- Ex 9.1
- Ex 9.2
- Ex 9.3
- Ex 9.4
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Examples
- Miscellaneous
Transcript
Example 14 The sum of first three terms of a G.P. is 13/12 and their product is β 1. Find the common ratio and the terms. Let the three terms in G.P. be π/π, a, ar here 1st term of G.P. = π/π 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 (β 1 βr βr2)/r = 13/12 12( -1 β r β r2 )= 13r -12 β 12r β 12r2 = 13r -12 - 12r - 12r2 β 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
