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1/4+1/28+1/70+1/(3n-2)*(3n+1)

Sum of series 1/4+1/28+1/70+1/(3n-2)*(3n+1)



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The solution

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  oo                               
 ___                               
 \  `                              
  \   /                    3*n + 1\
   )  |1/4 + 1/28 + 1/70 + -------|
  /   \                    3*n - 2/
 /__,                              
n = 1                              
$$\sum_{n=1}^{\infty} \left(\left(\frac{1}{70} + \left(\frac{1}{28} + \frac{1}{4}\right)\right) + \frac{3 n + 1}{3 n - 2}\right)$$
Sum(1/4 + 1/28 + 1/70 + (3*n + 1)/(3*n - 2), (n, 1, oo))
The radius of convergence of the power series
Given number:
$$\left(\frac{1}{70} + \left(\frac{1}{28} + \frac{1}{4}\right)\right) + \frac{3 n + 1}{3 n - 2}$$
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
$$a_{n} = \frac{3}{10} + \frac{3 n + 1}{3 n - 2}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty}\left(\frac{\left|{\frac{3}{10} + \frac{3 n + 1}{3 n - 2}}\right|}{\frac{3}{10} + \frac{3 n + 4}{3 n + 1}}\right)$$
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 1/4+1/28+1/70+1/(3n-2)*(3n+1)

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