Mister Exam

Sum of series 1/7n



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The solution

You have entered [src]
  oo   
 ___   
 \  `  
  \   n
   )  -
  /   7
 /__,  
n = 1  
$$\sum_{n=1}^{\infty} \frac{n}{7}$$
Sum(n/7, (n, 1, oo))
The radius of convergence of the power series
Given number:
$$\frac{n}{7}$$
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
$$a_{n} = \frac{n}{7}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty}\left(\frac{n}{7 \left(\frac{n}{7} + \frac{1}{7}\right)}\right)$$
Let's take the limit
we find
True

False
The rate of convergence of the power series
The answer [src]
oo
$$\infty$$
oo
Numerical answer
The series diverges
The graph
Sum of series 1/7n

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