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1+1/x+1/x^2++1/x^3+1/x^4+1/x^5+1/x^6+1/x^7+1/x^8+1/x^9+1/x^10

Sum of series 1+1/x+1/x^2++1/x^3+1/x^4+1/x^5+1/x^6+1/x^7+1/x^8+1/x^9+1/x^10



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The solution

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  oo                                                       
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\   `                                                      
 \    /    1   1    1    1    1    1    1    1    1     1 \
  \   |1 + - + -- + -- + -- + -- + -- + -- + -- + -- + ---|
  /   |    x    2    3    4    5    6    7    8    9    10|
 /    \        x    x    x    x    x    x    x    x    x  /
/___,                                                      
x = 2                                                      
$$\sum_{x=2}^{\infty} \left(\left(\left(\left(\left(\left(\left(\left(\left(\left(1 + \frac{1}{x}\right) + \frac{1}{x^{2}}\right) + \frac{1}{x^{3}}\right) + \frac{1}{x^{4}}\right) + \frac{1}{x^{5}}\right) + \frac{1}{x^{6}}\right) + \frac{1}{x^{7}}\right) + \frac{1}{x^{8}}\right) + \frac{1}{x^{9}}\right) + \frac{1}{x^{10}}\right)$$
Sum(1 + 1/x + 1/(x^2) + 1/(x^3) + 1/(x^4) + 1/(x^5) + 1/(x^6) + 1/(x^7) + 1/(x^8) + 1/(x^9) + 1/(x^10), (x, 2, oo))
The radius of convergence of the power series
Given number:
$$\left(\left(\left(\left(\left(\left(\left(\left(\left(1 + \frac{1}{x}\right) + \frac{1}{x^{2}}\right) + \frac{1}{x^{3}}\right) + \frac{1}{x^{4}}\right) + \frac{1}{x^{5}}\right) + \frac{1}{x^{6}}\right) + \frac{1}{x^{7}}\right) + \frac{1}{x^{8}}\right) + \frac{1}{x^{9}}\right) + \frac{1}{x^{10}}$$
It is a series of species
$$a_{x} \left(c x - x_{0}\right)^{d x}$$
- power series.
The radius of convergence of a power series can be calculated by the formula:
$$R^{d} = \frac{x_{0} + \lim_{x \to \infty} \left|{\frac{a_{x}}{a_{x + 1}}}\right|}{c}$$
In this case
$$a_{x} = 1 + \frac{1}{x} + \frac{1}{x^{2}} + \frac{1}{x^{3}} + \frac{1}{x^{4}} + \frac{1}{x^{5}} + \frac{1}{x^{6}} + \frac{1}{x^{7}} + \frac{1}{x^{8}} + \frac{1}{x^{9}} + \frac{1}{x^{10}}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{x \to \infty}\left(\frac{1 + \frac{1}{x} + \frac{1}{x^{2}} + \frac{1}{x^{3}} + \frac{1}{x^{4}} + \frac{1}{x^{5}} + \frac{1}{x^{6}} + \frac{1}{x^{7}} + \frac{1}{x^{8}} + \frac{1}{x^{9}} + \frac{1}{x^{10}}}{1 + \frac{1}{x + 1} + \frac{1}{\left(x + 1\right)^{2}} + \frac{1}{\left(x + 1\right)^{3}} + \frac{1}{\left(x + 1\right)^{4}} + \frac{1}{\left(x + 1\right)^{5}} + \frac{1}{\left(x + 1\right)^{6}} + \frac{1}{\left(x + 1\right)^{7}} + \frac{1}{\left(x + 1\right)^{8}} + \frac{1}{\left(x + 1\right)^{9}} + \frac{1}{\left(x + 1\right)^{10}}}\right)$$
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+1/x+1/x^2++1/x^3+1/x^4+1/x^5+1/x^6+1/x^7+1/x^8+1/x^9+1/x^10

    Examples of finding the sum of a series