How Can I Derive Sumations with Multiple Indices and Powers?

  • Thread starter jetoso
  • Start date
In summary, the conversation is about trying to figure out how to derive a complicated equation involving summations. The main task is to switch the order of summation and use a change of variables to simplify the equation. The author of the book does not provide much information on how to derive the equation, but it is considered trivial once the order of summation is switched and the variables are changed.
  • #1
jetoso
73
0
I have a hard time trying to figure it out how to derive the following sumations:

We know that:
P(z) = Sumation from j=0 to Infinity of [(Pj * (z^j)]
and
Q(z) = Sumation from j=0 to Infinity of [(Kj * ((z^j)]

Where j is a subindex for P and K, and a power for z.


Sumation from j=0 to Infinity of [ Sumation from i=0 to j+1 of [(z^j) * Pi * Kj-i+1] ]

Where i and j are a subindices for P and K, and a power for z.



I know that I have to play with the indices, but I have no clue. Any advice??
 
Mathematics news on Phys.org
  • #2
I may be missing something, but I can't see what your question is?
 
  • #3
Reply

Yes, you are right.
From the information above, it has to be simplified to:
[ (1/z) * P(z) * Q(z) ] - [ (1/z) * Po * Q(z) ]

The author of the book does not give much more information about how he derived this equation, but he says is trivial.
 
  • #4
The basic trick is to switch the order of summation. Then you will have two parts. The main part has i=1,inf with j=i-1,inf. The other part has i=0 with j=0,inf. For the main part let n=j-i+1 (replacing j), then n=0,inf. Put it all together and you should get the required answer.
 
  • #5
Sorry

I am sorry, but I still do not get it.
 
  • #6
Do you understand switching the order of summation?
Do you see the result of switching?
Do you understand the change of variables (n=)?
 

FAQ: How Can I Derive Sumations with Multiple Indices and Powers?

What is a problem with summations?

A problem with summations, also known as a summation problem, is a mathematical puzzle or challenge that involves finding the sum of a series of numbers or terms. It can involve various levels of complexity and may require different techniques to solve.

How do you solve a problem with summations?

The process for solving a problem with summations depends on the specific problem at hand. However, some common approaches include using formulas, breaking the sum into smaller parts, and using algebraic manipulation techniques. It is also important to accurately identify the pattern or relationship between the terms in the series.

What are some common types of problems with summations?

Some common types of problems with summations include arithmetic and geometric series, telescoping series, and infinite series. These problems may also involve concepts such as factorial notation, sequences, and series convergence and divergence.

Why are problems with summations important in science?

Problems with summations are important in science because they allow for the analysis and understanding of patterns and trends. In fields such as physics and engineering, summations are used to calculate quantities such as velocity, acceleration, and energy. They are also used in statistics to analyze data and make predictions.

What are some strategies for approaching a difficult problem with summations?

When faced with a difficult problem with summations, it can be helpful to break the sum into smaller parts, look for patterns, and try different techniques such as substitution and algebraic manipulation. It can also be beneficial to seek help from a tutor or consult with other experts in the field.

Back
Top