Multiplying summations?

  • Thread starter Luongo
  • Start date
  • #1
Luongo
120
0
1. on #1 c) of the homework:
http://www.math.ubc.ca/~oyilmaz/courses/m267/hmk3.pdf [Broken]
how do i multiply this summation?




Homework Equations





3. what i did was i multiplied the 2 expos and made on of the k indexes a 'm' instead and i got [tex]\sum ei(k+m)t[/tex]
 
Last edited by a moderator:

Answers and Replies

  • #2
praharmitra
311
1
[tex] \left( \sum_{k =1}^{N_1} f(k) \right) \left( \sum_{j=1}^{N_2} g(j) \right) = \sum_{k=1}^{N_1} \sum_{j=1}^{N_2} f(k)g(j) [/tex]

Can you try to see why the above is true?

Now in your problem, k is a dummy variable (meaning, that since it sums over, it doesn't matter if we call it k, or j). So we can replace the variable in the second summation, by j. Then you can apply the above formula.
 

Suggested for: Multiplying summations?

  • Last Post
Replies
3
Views
1K
  • Last Post
Replies
8
Views
3K
  • Last Post
Replies
9
Views
5K
  • Last Post
Replies
1
Views
2K
  • Last Post
Replies
5
Views
2K
  • Last Post
Replies
21
Views
3K
  • Last Post
Replies
26
Views
2K
  • Last Post
Replies
11
Views
4K
  • Last Post
Replies
3
Views
3K
  • Last Post
Replies
5
Views
2K
Top