Mister Exam

Sum of series e^(4n)



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The solution

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  oo      
 ___      
 \  `     
  \    4*n
  /   E   
 /__,     
n = 1     
n=1e4n\sum_{n=1}^{\infty} e^{4 n}
Sum(E^(4*n), (n, 1, oo))
The radius of convergence of the power series
Given number:
e4ne^{4 n}
It is a series of species
an(cxx0)dna_{n} \left(c x - x_{0}\right)^{d n}
- power series.
The radius of convergence of a power series can be calculated by the formula:
Rd=x0+limnanan+1cR^{d} = \frac{x_{0} + \lim_{n \to \infty} \left|{\frac{a_{n}}{a_{n + 1}}}\right|}{c}
In this case
an=1a_{n} = 1
and
x0=ex_{0} = - e
,
d=4d = 4
,
c=0c = 0
then
R4=~(e+limn1)R^{4} = \tilde{\infty} \left(- e + \lim_{n \to \infty} 1\right)
Let's take the limit
we find
False

False
The rate of convergence of the power series
1.07.01.52.02.53.03.54.04.55.05.56.06.502000000000000
The answer [src]
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The graph
Sum of series e^(4n)

    Examples of finding the sum of a series