Understanding Sequence Notation and Finding Next 5 Terms: Homework Help

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Homework Help Overview

The discussion revolves around a recurrence relation defined as a_{n+2}=3a_{n+1}-2a_n with initial conditions a_1=1 and a_2=1. Participants are tasked with finding the next five terms of the sequence.

Discussion Character

  • Exploratory, Conceptual clarification, Problem interpretation

Approaches and Questions Raised

  • Participants express confusion regarding the notation "a sub n" and the process of finding subsequent terms. Some suggest substituting values into the recurrence relation to compute terms, while others question whether all terms in the sequence are equal to 1.

Discussion Status

The discussion includes attempts to clarify the recurrence relation and its implications. Some participants have provided guidance on how to compute the next term, while others are exploring the nature of the sequence and whether it leads to a constant value.

Contextual Notes

There is a noted uncertainty about the implications of the recurrence relation, particularly regarding the values of the terms beyond the initial conditions. Participants are also navigating the challenge of understanding the notation and its application in this context.

cdotter
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Homework Statement


a_{n+2}=3a_{n+1}-2a_n[/itex]<br /> a_1=1, a_2=1<br /> Find the next 5 terms.<br /> <br /> <h2>Homework Equations</h2><br /> <br /> <br /> <br /> <h2>The Attempt at a Solution</h2><br /> I don&#039;t really understand the &quot;a sub n&quot; notation. Could someone do the next few terms so I can see how it&#039;s done?
 
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To find a3, for example, plug in n=1 into the first equation.

So, let n=1. Then,
a1+2 = a3 = 3a2 - 2a1 = 3(1) - 2(1) = 1
 
a_{1+2}=3a_{1+1} + 2a_1
a_3 = 3(1)-2(1) = 1?
 
cdotter said:

Homework Statement


a_{n+2}=3a_{n+1}-2a_n[/itex]<br /> a_1=1, a_2=1<br /> Find the next 5 terms.<br /> <br /> <h2>Homework Equations</h2><br /> <br /> <br /> <br /> <h2>The Attempt at a Solution</h2><br /> I don&#039;t really understand the &quot;a sub n&quot; notation.<br />
The terms in the sequence are {a<sub>1</sub>, a<sub>2</sub>, a<sub>3</sub>, ..., a<sub>n</sub>, a<sub>n+1</sub>, a<sub>n+2</sub>, ...}.<br /> <br /> The first formula says that to get the (n + 2)nd term in the sequence you need the preceding two terms, the (n + 1)st term and the nth term. <blockquote data-attributes="" data-quote="cdotter" data-source="post: 2668920" class="bbCodeBlock bbCodeBlock--expandable bbCodeBlock--quote js-expandWatch"> <div class="bbCodeBlock-title"> cdotter said: </div> <div class="bbCodeBlock-content"> <div class="bbCodeBlock-expandContent js-expandContent "> Could someone do the next few terms so I can see how it&#039;s done? </div> </div> </blockquote>Well, no, but maybe you can do them. You have a<sub>1</sub> = 1 and a<sub>2</sub> = 1. Use the first formula to get a<sub>3</sub>. Then when you have a<sub>3</sub>, use the formula again to find a<sub>4</sub>, and so on for as many terms as you need.
 
So any possible a_n always equals 1?
 
Last edited:
cdotter said:
a_{1+2}=3a_{1+1} + 2a_1
a_3 = 3(1)-2(1) = 1?
The formula is

a_{1+2}=3a_{1+1} - 2a_1
 
cdotter said:
So any possible a_n always equals 1?
For this sequence, yes.

A simpler and nonrecursive definition would be an = 1 for n = 1, 2, 3, ...
 
Mark44 said:
For this sequence, yes.

A simpler and nonrecursive definition would be an = 1 for n = 1, 2, 3, ...

Ok, thank you. I kept thinking I was missing something because it's stupid to ask for the next 5 terms when they're all equal to 1.
 

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