Interval of convergence with binomial coefficient

In summary, the interval of convergence for a series with binomial coefficient is the range of values for which the series will converge. The binomial coefficient can affect the interval of convergence by changing the value of the radius of convergence. It can be infinite, meaning the series will converge for all real values of x, or it can be a finite range of values. To determine the interval of convergence, the ratio test or root test can be used. The order of the binomial coefficient can also affect the interval of convergence, potentially decreasing the radius of convergence. However, this is not always the case and depends on the specific series and binomial coefficient being used.
  • #1
jetsetjoe
5
0

Homework Statement



Find the radius of converge of:

[tex]\sum[/tex]x[tex]^{}(n choose k)[/tex]

Homework Equations



Radius of converge = 1/limsup|an+1/an|, for power series: anx^n

The Attempt at a Solution




Tried rewriting (n choose k) as: n!/[k!(n-k)!]

but where do I go from here? How do I take out x^n?
 
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  • #2
How is the series defined?
Is it,
[tex]\sum_{n=k}^{\infty} x^{{n\choose k}}[/tex]


For example,
[tex]\sum_{n=0}^{\infty} x^{n!}[/tex]
Use the ratio test.
 

1. What is the interval of convergence for a series with binomial coefficient?

The interval of convergence for a series with binomial coefficient is the range of values for which the series will converge. It is typically expressed using inequalities, such as |x - a| < R, where a is the center of the series and R is the radius of convergence.

2. How is the interval of convergence affected by the binomial coefficient?

The binomial coefficient can affect the interval of convergence by changing the value of the radius of convergence. This is because the binomial coefficient can change the behavior of the series, making it either converge or diverge for certain values of x.

3. Can the interval of convergence for a series with binomial coefficient be infinite?

Yes, the interval of convergence for a series with binomial coefficient can be infinite. This means that the series will converge for all real values of x. However, it is also possible for the interval of convergence to be a finite range of values.

4. How can we determine the interval of convergence for a series with binomial coefficient?

To determine the interval of convergence for a series with binomial coefficient, we can use the ratio test or the root test. These tests involve finding the limit of the absolute value of the ratio or root of consecutive terms in the series. If this limit is less than 1, the series will converge for all values of x within the interval of convergence.

5. Is the interval of convergence affected by the order of the binomial coefficient?

Yes, the order of the binomial coefficient can affect the interval of convergence. As the order increases, the series may have a smaller radius of convergence, meaning that it will only converge for a smaller range of values for x. However, this is not always the case and it depends on the specific series and binomial coefficient being used.

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