
Algebra PreAlgebra and Basic Algebra Math Forum 
 LinkBack  Thread Tools  Display Modes 
March 5th, 2016, 04:48 AM  #1 
Member Joined: Aug 2015 From: Podgorica Posts: 61 Thanks: 0  Geometric sequence
Here is the problem, that I can not solve: The first term of a geometric series is 6, and the sum of the first 15 terms is 29. Find the common ratio. I have had a weird approach. I used the general formula and from there I found what is r(common ratio) equal to. I got this equation: 0=6r^1529r+23 Can you help me solve this equation? Is there any way of solving this problem, that makes more sense? 
March 5th, 2016, 05:41 AM  #2 
Global Moderator Joined: Dec 2006 Posts: 20,747 Thanks: 2133 
I don't think you can find exact expressions for the solutions. There are two relevant real roots (r = 1 doesn't count). r = 1.16150319 or 0.80044378 approximately. There are also 6 (conjugate) pairs of complex roots. 
March 5th, 2016, 06:18 AM  #3 
Member Joined: Aug 2015 From: Podgorica Posts: 61 Thanks: 0  Yes, that is the solution. How did you find it?
Last edited by skipjack; March 5th, 2016 at 08:44 AM. 
March 5th, 2016, 08:48 AM  #4 
Global Moderator Joined: Dec 2006 Posts: 20,747 Thanks: 2133 
I used WolframAlpha.


Tags 
geometric, sequence 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Geometric Sequence  scsims  Algebra  14  April 7th, 2015 08:25 AM 
geometric sequence  emohbe  Algebra  3  December 13th, 2010 10:00 PM 
Sum of geometric sequence  Eske939  Algebra  3  May 23rd, 2010 03:16 PM 
geometric sequence  Tafka  Calculus  2  May 3rd, 2010 08:48 AM 
what if geometric sequence + geometric sequence  frukoprof  Advanced Statistics  1  December 31st, 1969 04:00 PM 