Radius of Convergence Problem with Solution Attempt

In summary, the Radius of Convergence is a mathematical concept used to determine the range of values for which a power series will converge. It is calculated using the ratio test and is important for determining the validity of a series, estimating error, and understanding the behavior of a function. The radius cannot be negative and an infinite radius indicates that the series converges for all values of the variable.
  • #1
jegues
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3

Homework Statement



See figure attached for problem statement as well as my attempt.

Homework Equations





The Attempt at a Solution



See 2nd figure attached.

I don't know how to rid myself of that last n! I've got kicking around in the numerator.

Any ideas?
 

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  • #2
Check your an+1 term. The [(n+1)!] should be squared.
 
  • #3
jav said:
Check your an+1 term. The [(n+1)!] should be squared.

Doh!

Thank you!
 
  • #4
Just to make sure I finished the question off right, we should find that R = -1, correct?

Then the open interval of convergence is,

[tex]|x-7| < -1[/tex]

or [tex] 1 < x-7 < -1[/tex] or [tex] 8 < x < 6[/tex]
 

FAQ: Radius of Convergence Problem with Solution Attempt

What is the Radius of Convergence?

The Radius of Convergence is a mathematical concept used in power series to determine the range of values for which the series will converge. It is denoted by the letter R and is the distance from the center of the series to the nearest point where the series converges.

How is the Radius of Convergence calculated?

The Radius of Convergence is calculated using the ratio test, which involves taking the limit of the absolute value of the ratio of the n+1 term to the nth term as n approaches infinity. If the limit is less than 1, the series converges. If the limit is greater than 1, the series diverges. If the limit is equal to 1, the test is inconclusive and another method must be used to determine the convergence of the series.

What does it mean if the Radius of Convergence is infinite?

If the Radius of Convergence is infinite, it means that the series converges for all values of the variable. This is known as a convergent power series. In other words, the series will continue to converge as more terms are added, regardless of the value of the variable.

Can the Radius of Convergence be negative?

No, the Radius of Convergence cannot be negative. It represents a distance, so it must be a positive value. If the radius is negative, it can be changed to a positive value by taking the absolute value of the radius. However, a negative radius does not make mathematical sense in the context of power series convergence.

Why is the Radius of Convergence important?

The Radius of Convergence is important in determining the validity of a power series and the values for which it will converge. It also allows for the estimation of the error in approximating a function using a power series. Additionally, the radius can provide insight into the behavior of the function near its center point and can be used to find the interval of convergence for the series.

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