Summing a series on an interval of convergence

In summary, a series on an interval of convergence is a mathematical concept where a sequence of numbers is added together over a specified range. This range, known as the interval of convergence, determines the set of values for which the series will converge. The interval of convergence can be determined using the Ratio Test, which compares the limit of the absolute value of the ratio of consecutive terms to a specific value. If the limit is less than 1, the series will converge within the interval. If it is greater than 1, the series will diverge. If the absolute value of the ratio of consecutive terms is equal to 1, another test must be used to determine convergence. A series can converge on its endpoints, but may not converge for
  • #1
c.dube
27
0

Homework Statement


Find the interval of convergence of the series and, within this interval, the sum of the series as a function of x.
[tex]\sum^{\infty}_{n=0}\frac{(x-1)^{2n}}{4^n}[/tex]

Homework Equations


N/A

The Attempt at a Solution


Finding the interval is easy, using the ratio test it reduces down to
[tex]|\frac{(x-1)^{2}}{4}|<1[/tex]
[tex]-1<x<3[/tex]

However, I have no idea how to do the second part. Any help?
 
Last edited:
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  • #2
1- You should check the end points to decide the interval.
2- For the sum, I think you know something called "geomtric series", right?
 
  • #3
Duh! Thanks.
 

1. What is a series on an interval of convergence?

A series on an interval of convergence is a mathematical concept in which a sequence of numbers is added together over a specific range or interval. This range is known as the interval of convergence and determines the set of values for which the series will converge, or approach a finite value.

2. How do you determine the interval of convergence for a series?

The interval of convergence for a series can be determined by using the Ratio Test, which compares the limit of the absolute value of the ratio of consecutive terms in the series to a specific value. If this limit is less than 1, then the series will converge within the specified interval. If the limit is greater than 1, the series will diverge.

3. What happens if the absolute value of the ratio of consecutive terms is equal to 1?

If the absolute value of the ratio of consecutive terms is equal to 1, then the Ratio Test is inconclusive and another method, such as the Root Test, must be used to determine the convergence of the series.

4. Can a series converge on its endpoints?

Yes, a series can converge on its endpoints. This means that the series will converge when the value of the variable in the series is equal to the upper or lower limit of the interval of convergence. However, it is important to note that the series may or may not converge for all values within the interval of convergence.

5. What is the significance of the interval of convergence in a series?

The interval of convergence is significant because it determines the set of values for which the series will converge. This allows us to determine the range of values for which the series is valid and can be used to approximate a specific value. It also helps in determining the convergence or divergence of the series as a whole.

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