Summing a Sequence: Finite or Infinite?

  • Thread starter Firepanda
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In summary: This showed that the terms approach a positive number as n increases. Therefore, the series diverges. In summary, the person has created two similar summations for their coursework and is trying to determine if they are finite or infinite. The first summation was easy to show as infinite, but with the addition of another term, they are unsure how to proceed. They ask for help and someone suggests taking the limit of the nth term to determine if the series approaches a positive number, which would indicate divergence.
  • #1
Firepanda
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I've created two summations for my coursework, now I need to show whether or not the summations are finite or infinite.

The 2 summations are very similar:

2meqrl0.png


With the n/2 removed it was easy enough to show the sum was equal to 1 [edit: I now realize I may have this wrong], now with the n/2 term added I really have no idea where to start.

Any help appreciated, thanks.

Edit: I can see my writing may not be legible, 1's in the pic are straight vertical lines, some of the 2's may look like 1's, but they are 2's.
 
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  • #2
Firepanda said:
I've created two summations for my coursework, now I need to show whether or not the summations are finite or infinite.

The 2 summations are very similar:

2meqrl0.png


With the n/2 removed it was easy enough to show the sum was equal to 1 [edit: I now realize I may have this wrong], now with the n/2 term added I really have no idea where to start.

Any help appreciated, thanks.

Edit: I can see my writing may not be legible, 1's in the pic are straight vertical lines, some of the 2's may look like 1's, but they are 2's.

For the first one, I found that the terms in the sequence approach a positive number. This is enough to convince me that the first series diverges.
 
  • #3
Mark44 said:
For the first one, I found that the terms in the sequence approach a positive number. This is enough to convince me that the first series diverges.

Thanks for the reply!

Does this mean it sums to infinity?

What were your steps to find that it approaches a positive number?
 
  • #4
Firepanda said:
Thanks for the reply!

Does this mean it sums to infinity?
Your textbook should have definitions for the terms converges and diverges.
Firepanda said:
What were your steps to find that it approaches a positive number?
I took the limit of the nth term in the sequence.
 

1. What is a sequence?

A sequence is a set of numbers that follow a specific pattern or rule. The numbers in a sequence are called terms, and they can be arranged in a specific order.

2. What is the difference between a finite and an infinite sequence?

A finite sequence has a limited number of terms, while an infinite sequence has an unlimited number of terms. In other words, a finite sequence has an ending point, while an infinite sequence does not.

3. How do you sum a finite sequence?

To sum a finite sequence, you can use the formula: Sn = (n/2)(a1 + an), where n is the number of terms in the sequence, a1 is the first term, and an is the last term.

4. Can an infinite sequence be summed?

Yes, an infinite sequence can be summed as long as it meets certain criteria. For example, if the terms in the sequence approach a specific value as the number of terms increases, the sequence can be summed.

5. Why is it important to determine if a sequence is finite or infinite before attempting to sum it?

It is important to determine if a sequence is finite or infinite because the method used to sum each type of sequence is different. Attempting to use the wrong method can lead to incorrect results.

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