Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

The problome is rewriten here: $\sum_{i=0}^k \frac{((i-k)a)^i b^{k-i}}{i!}$ where $0<a<1$, k is an integer larger than 1.

I came to this equation when i try to find some probability. I have tried some formulas on permutation and combination, fractional, but with little improvement.

I hope you can give me some sugestions! Thanks a lot!

share|cite|improve this question
    
What is the question? How do you want to simplify this? – glebovg Oct 29 '12 at 3:05
    
It is equivalent to $\sum_{i=0}^k\prod_{j=1}^i (1-\frac{k}{i})a$. Is this helpful? – Severals-user45972 Oct 29 '12 at 3:07
    
I want to get an expression without factorials or \sum operations. – Severals-user45972 Oct 29 '12 at 3:09
    
Does [] mean floor or brackets? – glebovg Oct 29 '12 at 3:13
    
They are only brackets. I have replaced [] with (). – Severals-user45972 Oct 29 '12 at 3:14

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.