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sqrt(n/n^3+2*n+9)

Sum of series sqrt(n/n^3+2*n+9)



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The solution

You have entered [src]
  oo                     
____                     
\   `                    
 \         ______________
  \       / n            
   )     /  -- + 2*n + 9 
  /     /    3           
 /    \/    n            
/___,                    
n = 1                    
$$\sum_{n=1}^{\infty} \sqrt{\left(2 n + \frac{n}{n^{3}}\right) + 9}$$
Sum(sqrt(n/n^3 + 2*n + 9), (n, 1, oo))
The radius of convergence of the power series
Given number:
$$\sqrt{\left(2 n + \frac{n}{n^{3}}\right) + 9}$$
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
$$a_{n} = \sqrt{2 n + 9 + \frac{1}{n^{2}}}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty}\left(\frac{\sqrt{2 n + 9 + \frac{1}{n^{2}}}}{\sqrt{2 n + 11 + \frac{1}{\left(n + 1\right)^{2}}}}\right)$$
Let's take the limit
we find
True

False
The rate of convergence of the power series
The answer [src]
  oo                     
____                     
\   `                    
 \         ______________
  \       /     1        
   )     /  9 + -- + 2*n 
  /     /        2       
 /    \/        n        
/___,                    
n = 1                    
$$\sum_{n=1}^{\infty} \sqrt{2 n + 9 + \frac{1}{n^{2}}}$$
Sum(sqrt(9 + n^(-2) + 2*n), (n, 1, oo))
The graph
Sum of series sqrt(n/n^3+2*n+9)

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