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(-1)^n/sqrt(n)

Sum of series (-1)^n/sqrt(n)



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The solution

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

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