Mister Exam

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  • Sum of series:
  • (-1)^n (-1)^n
  • 1/(n(n+3)) 1/(n(n+3))
  • (3^n-4^n)/12^n (3^n-4^n)/12^n
  • 1/((n+14)(n+15)) 1/((n+14)(n+15))
  • Identical expressions

  • (x+ three)^n/ two ^nsqrt(n^ four + four) one /n^ two
  • (x plus 3) to the power of n divide by 2 to the power of n square root of (n to the power of 4 plus 4)1 divide by n squared
  • (x plus three) to the power of n divide by two to the power of n square root of (n to the power of four plus four) one divide by n to the power of two
  • (x+3)^n/2^n√(n^4+4)1/n^2
  • (x+3)n/2nsqrt(n4+4)1/n2
  • x+3n/2nsqrtn4+41/n2
  • (x+3)^n/2^nsqrt(n⁴+4)1/n²
  • (x+3) to the power of n/2 to the power of nsqrt(n to the power of 4+4)1/n to the power of 2
  • x+3^n/2^nsqrtn^4+41/n^2
  • (x+3)^n divide by 2^nsqrt(n^4+4)1 divide by n^2
  • Similar expressions

  • (x-3)^n/2^nsqrt(n^4+4)1/n^2
  • (x+3)^n/2^nsqrt(n^4-4)1/n^2

Sum of series (x+3)^n/2^nsqrt(n^4+4)1/n^2



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The solution

You have entered [src]
   oo                       
______                      
\     `                     
 \             n    ________
  \     (x + 3)    /  4     
   \    --------*\/  n  + 4 
    \       n               
    /      2                
   /    --------------------
  /               2         
 /               n          
/_____,                     
 n = 1                      
$$\sum_{n=1}^{\infty} \frac{\frac{\left(x + 3\right)^{n}}{2^{n}} \sqrt{n^{4} + 4}}{n^{2}}$$
Sum((((x + 3)^n/2^n)*sqrt(n^4 + 4))/n^2, (n, 1, oo))
The radius of convergence of the power series
Given number:
$$\frac{\frac{\left(x + 3\right)^{n}}{2^{n}} \sqrt{n^{4} + 4}}{n^{2}}$$
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
$$a_{n} = \frac{2^{- n} \sqrt{n^{4} + 4}}{n^{2}}$$
and
$$x_{0} = -3$$
,
$$d = 1$$
,
$$c = 1$$
then
$$R = -3 + \lim_{n \to \infty}\left(\frac{2^{- n} 2^{n + 1} \left(n + 1\right)^{2} \sqrt{n^{4} + 4}}{n^{2} \sqrt{\left(n + 1\right)^{4} + 4}}\right)$$
Let's take the limit
we find
$$R = -1$$
The answer [src]
  oo                           
_____                          
\    `                         
 \                     ________
  \     -n        n   /      4 
   \   2  *(3 + x) *\/  4 + n  
   /   ------------------------
  /                2           
 /                n            
/____,                         
n = 1                          
$$\sum_{n=1}^{\infty} \frac{2^{- n} \sqrt{n^{4} + 4} \left(x + 3\right)^{n}}{n^{2}}$$
Sum(2^(-n)*(3 + x)^n*sqrt(4 + n^4)/n^2, (n, 1, oo))

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