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Sum of series (xi+2)



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The solution

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  oo           
 __            
 \ `           
  )   (x*i + 2)
 /_,           
i = 1          
$$\sum_{i=1}^{\infty} \left(i x + 2\right)$$
Sum(x*i + 2, (i, 1, oo))
The radius of convergence of the power series
Given number:
$$i x + 2$$
It is a series of species
$$a_{i} \left(c x - x_{0}\right)^{d i}$$
- power series.
The radius of convergence of a power series can be calculated by the formula:
$$R^{d} = \frac{x_{0} + \lim_{i \to \infty} \left|{\frac{a_{i}}{a_{i + 1}}}\right|}{c}$$
In this case
$$a_{i} = i x + 2$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{i \to \infty} \left|{\frac{i x + 2}{x \left(i + 1\right) + 2}}\right|$$
Let's take the limit
we find
True

False
The answer [src]
oo + oo*x
$$\infty x + \infty$$
oo + oo*x

    Examples of finding the sum of a series