Shifted Factorial Homework: Showing \sum_{n=0}^{\infty}

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In summary, the conversation discusses the proof of the summation formula for the series, where the Pochhammer symbol and shifted factorial are defined. The conversation also clarifies that for n=0 and n=1, the terms of the sum equal 1 and a, respectively. The formula can be extended to higher values of n.
  • #1
Ted123
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Homework Statement



I've got to show [tex]\sum_{n=0}^{\infty} \frac{(a)_n(-1)_n}{(c)_n n!} = \frac{c-a}{c}[/tex]
where
[tex]\displaystyle (a)_n = \frac{\Gamma(a+n)}{\Gamma(a)} = a(a+1)...(a+n-1)[/tex]
is the shifted factorial (Pochhammer symbol).

The Attempt at a Solution



I've been informed that [tex](-1)_n = 0\;\;\;\;\;\;\forall\;\;n\geq 2[/tex]
So the sum has only 2 terms for n=0 and n=1, but what do e.g. [tex](-1)_0\,,\,(-1)_1\,,\,(a)_0\,,\,(a)_1[/tex] equal?
 
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  • #2
Hi Ted123! :smile:

look at the definition of (a)n

(a)0 obviously = 1 for all a (including (-1)0 = 1),

and (a)1 = … ? :wink:
 
  • #3
tiny-tim said:
Hi Ted123! :smile:

look at the definition of (a)n

(a)0 obviously = 1 for all a (including (-1)0 = 1),

and (a)1 = … ? :wink:

So would (a)1 = a, and (-1)1 = -1 ?

So the 2 terms of the sum give [tex]1 - \frac{a}{c} = \frac{c-a}{c}[/tex]
Incidentally would (a)2 = a(a+1), (a)3 = a(a+1)(a+2) etc.?
 
Last edited:
  • #4
yes yes yes yes and yes :smile:
 

Related to Shifted Factorial Homework: Showing \sum_{n=0}^{\infty}

1. What is the concept of Shifted Factorial Homework?

Shifted Factorial Homework is a mathematical concept that involves calculating the sum of a series of terms, where each term is the product of a shifted factorial and a variable raised to a power. The shifted factorial is denoted by the exclamation mark (!) and represents the product of all the numbers from 1 up to a certain number minus the shift value. This concept is commonly used in statistics and combinatorics.

2. What is the significance of the summation symbol (∑) in the equation?

The summation symbol (∑) indicates that we are adding up a series of terms. In this case, the symbol is followed by the variable n, which represents the number of terms in the series. The subscript n=0 indicates that we are starting the series from the 0th term.

3. What is the purpose of the upper and lower limits in the summation symbol?

The lower limit of the summation symbol (n=0) indicates where the series begins, while the upper limit (n=∞) indicates where the series ends. In this case, the series continues indefinitely, which is why the upper limit is represented by the infinity symbol (∞).

4. How can the shifted factorial be calculated?

The shifted factorial can be calculated by multiplying all the numbers from 1 up to the given number minus the shift value. For example, if we have a shifted factorial of 5!, the calculation would be 5 x 4 x 3 x 2 x 1 = 120. If the shift value is 2, then we would subtract 2 from the given number (5-2=3) and multiply all the numbers up to 3, resulting in 3 x 2 x 1 = 6. Therefore, 5! with a shift value of 2 would be equal to 120/6 = 20.

5. How is the concept of Shifted Factorial Homework applied in real-life situations?

The concept of Shifted Factorial Homework is commonly used in statistics and combinatorics to calculate the number of possible combinations or permutations of a given set of elements. It is also used in probability calculations, such as finding the probability of a certain number of events occurring in a given sequence. Additionally, it can be applied in various fields such as engineering, computer science, and economics to solve complex problems involving combinations and permutations.

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