Conceptual question regarding sum of series

In summary, the discussion revolves around whether the sum of two divergent series, a_n and b_n, will necessarily result in a divergent sum of (a_n + b_n). It is concluded that this is not always the case, as there are examples where the sum of (a_n + b_n) is 0 and therefore convergent.
  • #1
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Homework Statement


If the sum(a_n) and the sum(b_n) are both divergent, is the sum(a_n + b_n) necessarily divergent?


The Attempt at a Solution


At first I thought it must be divergent, but then I asked, what if a_n is 1/n and b_n is -1/n... then their sum would be 0.

Does this logic make sense? And if so, would it imply that sum(a_n + b_n)=0, and is therefore convergent?
 
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  • #2
Your logic is correct. We can even get simpler examples. a_n = n, b_n = -n. Each diverges individually, but a_n + b_n = 0 for every term. And yes, it implies the sum of (a_n + b_n) is 0, convergent.
 

FAQ: Conceptual question regarding sum of series

What is a "sum of series" in mathematics?

A sum of series is a mathematical concept that involves adding together a sequence of numbers or terms in a specific order. The result of this addition is called the "sum" of the series.

How do you calculate the sum of a series?

The sum of a series can be calculated by adding together all the terms in the series. This can be done manually by hand or with the use of a calculator. There are also specific formulas and methods for calculating the sum of different types of series, such as arithmetic and geometric series.

What is the difference between an infinite series and a finite series?

An infinite series is a series that has an infinite number of terms, meaning it does not have an end point. A finite series, on the other hand, has a specific number of terms and therefore has an end point. Calculating the sum of an infinite series can be more complex than a finite series, as the number of terms to be added is infinite.

Can the sum of a series be negative?

Yes, the sum of a series can be negative. This can happen when the individual terms in the series alternate between positive and negative values, resulting in a net negative sum. Additionally, some series have a negative value as the starting term, which can also lead to a negative sum.

What is the significance of the sum of a series in mathematics?

The sum of a series plays an important role in various mathematical concepts and applications. It is used to find the total value of a sequence of numbers, and can also be used to represent real-world situations such as compound interest or population growth. Additionally, the sum of a series is often used in calculus and other advanced mathematical fields.

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