Limit of Infinite Series | Solving y = (2n+3n)/4n | Homework Statement

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Homework Help Overview

The discussion revolves around finding the limit of an infinite series, specifically the expression y = (2n + 3n) / 4n as n approaches infinity. Participants are exploring the behavior of this series and its components.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Some participants attempt to express the series in terms of geometric series and question how to find the sum of these series. Others express uncertainty about the convergence of areas in a related geometric problem involving inscribed shapes.

Discussion Status

The discussion includes attempts to clarify the nature of the series and the limits involved. Some guidance has been offered regarding geometric series, while participants are also exploring the implications of decreasing areas in a different context. There is a mix of understanding and confusion regarding the convergence of these areas.

Contextual Notes

Participants are working under the constraints of homework rules, with one problem being a bonus question from a test. There is a noted lack of clarity in the second problem regarding what specifically is being summed or limited.

steve2212
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Homework Statement


Find the limit of the sum of:

y = (2n + 3n) / 4n

The Attempt at a Solution



as n-> infinity, y approaches 0. I don't know where to proceed from here.
 
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It's 2^n/4^n+3^n/4^n=(2/4)^n+(3/4)^n. It's two separate geometric series. Can you deal with those?
 
Dick said:
It's 2^n/4^n+3^n/4^n=(2/4)^n+(3/4)^n. It's two separate geometric series. Can you deal with those?

Ya I got that but I don't know how to find the sum of an infinite geometric series
 
steve2212 said:
Ya I got that but I don't know how to find the sum of an infinite geometric series

That's regrettable. Then you should probably try to look it up in your text or online. It's pretty basic.
 
Oh sorry I'm stupid, I remembered how haha.

Since you're here I also have another hard one.

A circle is inscribed in a triangle, a square is inscribed in that circle, a circle is inscribed is that square, a pentagon is inscribed in that circle, the trend continues with the degree going up.

How do I proceed to solve this quesiton? I need to find t he sum of the limit
 
steve2212 said:
Oh sorry I'm stupid, I remembered how haha.

Since you're here I also have another hard one.

A circle is inscribed in a triangle, a square is inscribed in that circle, a circle is inscribed is that square, a pentagon is inscribed in that circle, the trend continues with the degree going up.

How do I proceed to solve this quesiton? I need to find t he sum of the limit

The first one wasn't hard. That one probably is. What are to trying to find the sum or the limit of? The areas, or the perimeters or the radii, or what? Not that I know the answer. But your question isn't even clear.
 
The limit of the sum of the area. Sorry forgot that detail.
 
steve2212 said:
The limit of the sum of the area. Sorry forgot that detail.

The sum of the areas of ALL of the geometric figures? I think it's pretty likely it diverges. Mostly gut feeling. Is this for a class, or is this your own creation? It's way out of scale with the difficulty of your first problem.
 
It was a bonus question on our test yesterday. Yup we need the limit of the sum of all of the areas. I know that the areas of the figures approach to 0 that's easy.
 
  • #10
How do you know the areas approach zero? Sure, they decrease. But that doesn't convince me that they approach zero. Do you know this has a simple solution? Because I'm sure not seeing it.
 
  • #11
Dick said:
How do you know the areas approach zero? Sure, they decrease. But that doesn't convince me that they approach zero. Do you know this has a simple solution? Because I'm sure not seeing it.

Area can't be negative, and area decreases, it has to approach 0. Right?
 
  • #12
steve2212 said:
Area can't be negative, and area decreases, it has to approach 0. Right?

Nope. 1+1/n is a positive decreasing sequence but it doesn't approach 0. It approaches 1.
 
  • #13
Sorry where do you get 1+ 1/n?
 
  • #14
steve2212 said:
Sorry where do you get 1+ 1/n?

It's just an example of a sequence that decreases but doesn't approach zero.
 

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