My Math Forum  

Go Back   My Math Forum > High School Math Forum > Algebra

Algebra Pre-Algebra and Basic Algebra Math Forum


Reply
 
LinkBack Thread Tools Display Modes
January 21st, 2010, 03:52 PM   #1
Newbie
 
Joined: Jan 2010

Posts: 8
Thanks: 0

Sequence Question

Kind of new to this site, and don't know if this is the right side, but anyways I'm having trouble with this arithmetic sequence question that is part of my culminating task.

If the sum of 'n' terms of an arithmetic sequence is 1/2(n^2+5n) find an expression for the 'k'th term.

I'd appreciate it if anyone can show me the steps to solve this question.
ExIsTaNcE is offline  
 
January 21st, 2010, 04:47 PM   #2
Senior Member
 
Joined: Feb 2009
From: Adelaide, Australia

Posts: 1,519
Thanks: 3

Re: Sequence Question

To find the first term, let n=1 and apply the formula.
To find the second term, let n=2, apply the formula, and subtract the first term.
You now have enough information to deduce the sequence.

In general, the sum of n terms, with the first term equal to a, will be
(a+0b)+(a+1b)+(a+2b)+(a+3b)+...+(a+(n-1)b)
= an + Żn(n-1)b
so you can also equate coefficients.
aswoods is offline  
January 21st, 2010, 04:56 PM   #3
Newbie
 
Joined: Jan 2010

Posts: 8
Thanks: 0

Re: Sequence Question

ok so the sequence is 3,4,5,6...

But what is it meant by the kth term?
ExIsTaNcE is offline  
January 21st, 2010, 05:28 PM   #4
Global Moderator
 
greg1313's Avatar
 
Joined: Oct 2008
From: London, Ontario, Canada - The Forest City

Posts: 7,854
Thanks: 1078

Math Focus: Elementary mathematics and beyond
Re: Sequence Question

The kth term is any term one wishes to choose. Since the sequence is 3, 4, 5, 6, . . . an expression for the kth term would be k + 2.
greg1313 is offline  
January 22nd, 2010, 12:37 AM   #5
Global Moderator
 
Joined: Dec 2006

Posts: 19,519
Thanks: 1746

The sum of k terms is (k + 5k)/2.
The sum of (k - 1) terms is ((k - 1) + 5(k - 1))/2.
By subtraction, the kth term is (2k - 1 + 5)/2, i.e., k + 2.
skipjack is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
question, sequence



Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Sequence and series question Cryptnar Real Analysis 4 September 29th, 2012 12:07 PM
Recursive Sequence Question Becarev Real Analysis 1 February 11th, 2012 08:17 AM
another sequence question hermanni Real Analysis 0 February 13th, 2011 12:52 PM
sequence question rose3 Real Analysis 2 December 31st, 2009 05:35 AM
Sequence Question adidasballa95 Algebra 3 May 8th, 2009 08:48 AM





Copyright © 2018 My Math Forum. All rights reserved.