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nln^2(3n)

Sum of series nln^2(3n)



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The solution

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  oo             
 ___             
 \  `            
  \        2     
  /   n*log (3*n)
 /__,            
n = 1            
$$\sum_{n=1}^{\infty} n \log{\left(3 n \right)}^{2}$$
Sum(n*log(3*n)^2, (n, 1, oo))
The radius of convergence of the power series
Given number:
$$n \log{\left(3 n \right)}^{2}$$
It is a series of species
$$a_{n} \left(c x - x_{0}\right)^{d n}$$
- power series.
The radius of convergence of a power series can be calculated by the formula:
$$R^{d} = \frac{x_{0} + \lim_{n \to \infty} \left|{\frac{a_{n}}{a_{n + 1}}}\right|}{c}$$
In this case
$$a_{n} = n \log{\left(3 n \right)}^{2}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty}\left(\frac{n \log{\left(3 n \right)}^{2}}{\left(n + 1\right) \log{\left(3 n + 3 \right)}^{2}}\right)$$
Let's take the limit
we find
True

False
The rate of convergence of the power series
Numerical answer
The series diverges
The graph
Sum of series nln^2(3n)

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