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((7n+5)/(2n))^n

Sum of series ((7n+5)/(2n))^n



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The solution

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  oo            
____            
\   `           
 \             n
  \   /7*n + 5\ 
  /   |-------| 
 /    \  2*n  / 
/___,           
n = 1           
$$\sum_{n=1}^{\infty} \left(\frac{7 n + 5}{2 n}\right)^{n}$$
Sum(((7*n + 5)/((2*n)))^n, (n, 1, oo))
The radius of convergence of the power series
Given number:
$$\left(\frac{7 n + 5}{2 n}\right)^{n}$$
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
$$a_{n} = \left(\frac{7 n + 5}{2 n}\right)^{n}$$
and
$$x_{0} = 0$$
,
$$d = 0$$
,
$$c = 1$$
then
$$1 = \lim_{n \to \infty}\left(\left(\frac{7 n + 5}{2 n}\right)^{n} \left(\frac{7 n + 12}{2 \left(n + 1\right)}\right)^{- n - 1}\right)$$
Let's take the limit
we find
False

False

False
The rate of convergence of the power series
The answer [src]
  oo            
____            
\   `           
 \             n
  \   /5 + 7*n\ 
  /   |-------| 
 /    \  2*n  / 
/___,           
n = 1           
$$\sum_{n=1}^{\infty} \left(\frac{7 n + 5}{2 n}\right)^{n}$$
Sum(((5 + 7*n)/(2*n))^n, (n, 1, oo))
The graph
Sum of series ((7n+5)/(2n))^n

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