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2i^2-9i+4

Sum of series 2i^2-9i+4



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The solution

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  oo                  
 ___                  
 \  `                 
  \   /   2          \
  /   \2*i  - 9*i + 4/
 /__,                 
i = 1                 
$$\sum_{i=1}^{\infty} \left(\left(2 i^{2} - 9 i\right) + 4\right)$$
Sum(2*i^2 - 9*i + 4, (i, 1, oo))
The radius of convergence of the power series
Given number:
$$\left(2 i^{2} - 9 i\right) + 4$$
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
$$a_{i} = 2 i^{2} - 9 i + 4$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{i \to \infty} \left|{\frac{2 i^{2} - 9 i + 4}{9 i - 2 \left(i + 1\right)^{2} + 5}}\right|$$
Let's take the limit
we find
True

False
The rate of convergence of the power series
Numerical answer
The series diverges
The graph
Sum of series 2i^2-9i+4

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