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!

Why operation * not defined in Q

  1. Jan 24, 2013 #1
    1. The problem statement, all variables and given/known data

    Show that l/m * k/n = (l+k)/(m2+n2) can not be defined as an operation in Q when l,k € Z and m, n € Z\{0}

    I do not know what is the issue here? Should I know something about Q that this not fulfilled by the operation *?
     
  2. jcsd
  3. Jan 24, 2013 #2

    jbunniii

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Hint: What happens if you negate [itex]l[/itex] and [itex]m[/itex]?
     
  4. Jan 24, 2013 #3
    Ok.. So the same operation can produce two different results??

    So that l/m * k/n = (l+k)/(m2+n2) ≠ (-l+k)/((-m)2+n2) = -l/-m * k/n = l/m * k/n
     
  5. Jan 24, 2013 #4

    jbunniii

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    That's right, so the operation is not well defined.
     
  6. Jan 24, 2013 #5
    Thank you very much jbunniii! Helped me a lot. I think we'll meet again.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Why operation * not defined in Q
Loading...