1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Factorials approximation problem

  1. Feb 25, 2008 #1
    1. The problem statement, all variables and given/known data
    How is,

    [(N+Q)!Q!]/[(Q+1)!(N+Q-1)!] equal to (N+Q)/(Q+1) when N,Q>>1 ??

    It looks like the Q!/(N+Q-1)! cancels but i don't see how, im going from my lecturers notes here.
    2. Relevant equations

    3. The attempt at a solution
    Last edited: Feb 25, 2008
  2. jcsd
  3. Feb 25, 2008 #2
    Break it up - look at the fraction as

    [tex]\frac{Q!}{(Q+1)!} \cdot \frac{(N+Q)!}{(N+Q-1)!}[/tex]

    For the first fraction, ask yourself "what number you would multiply [itex]Q![/itex] by to get [itex](Q+1)![/itex]"?

    Do a similar analysis for the second fraction.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Factorials approximation problem
  1. Simplifying Factorials (Replies: 2)

  2. Factorial Equation (Replies: 10)