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Sum of series/ 1-1/x^2

Sum of series 1-1/x^2


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The solution

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n = 1
$$\sum_{n=1}^{\infty} \left(1 - \frac{1}{x^{2}}\right)$$ 
Sum(1 - 1/x^2, (n, 1, oo))
The radius of convergence of the power series
Given number:
$$1 - \frac{1}{x^{2}}$$
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
$$a_{n} = 1 - \frac{1}{x^{2}}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty} 1$$
Let's take the limit
we find
True

False
The answer [src] 
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$$\infty \left(1 - \frac{1}{x^{2}}\right)$$ 
oo*(1 - 1/x^2)

    Examples of finding the sum of a series

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