1. Limited time only! Sign up for a free 30min personal 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!

Indepedent Variables

  1. May 18, 2013 #1
    we have X,Y variables and we have f(m,n)=P(X=m,Y=n)=C*((1/(a*m*n+15*m+11*n+8))^2)
    for what value of a X,Y are indepedent? ( its not necessery to calculate C)

    i know that f(m,n)=f(m)*f(n) if X,Y are independent but how i am gonna use this for calculate a?
  2. jcsd
  3. May 18, 2013 #2

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    Never write what you did: you are using the same symbol (f) to mean three different things in the same problem. Use three different names, such as f(m,n) = g(m) * h(n).

    Anyway, you need to find a value of 'a' that makes the denominator factor into a function of n alone times a factor of m alone.
  4. May 18, 2013 #3
    i will estimate (a*m*n+15*m+11*n+8)^2) ? if i will do it i find 10 terms
  5. May 18, 2013 #4


    User Avatar
    Science Advisor
    Homework Helper

    Parispart, follow the advice
  6. May 18, 2013 #5
    i understand that i have to find a factor of n times a factor of n but i try to think how to do it using the 'a'
  7. May 19, 2013 #6


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member
    2016 Award

    When you have found a, what do you think the factors will look like, in general terms? Can you write a generic form for those factors, using some other unknown constants?
  8. May 19, 2013 #7


    User Avatar
    Science Advisor
    Homework Helper

    Hi ParisSpart! :smile:

    (just got up :zzz:)
    Hint: if it was 1/(amn + m + n + 1)2,

    how would you choose a so you could factor that? :wink:

    (and what would the factors be?)
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted

Similar Discussions: Indepedent Variables
  1. Exponential variables (Replies: 4)

  2. 2 variables! (Replies: 7)

  3. Change of variable (Replies: 6)

  4. Random variables (Replies: 5)

  5. Free variable (Replies: 5)