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Set theory help !

  1. Oct 16, 2012 #1
    we have E=(a+b)/ab (a,b)EN*
    1/ prove that E C ]0,2] (i already duid that )
    2/ is ]0,2] E E? shelp me in this one!


    2. Relevant equations



    3. The attempt at a solution
    x [itex]\in[/itex] ]0,2] [itex]\Rightarrow[/itex] x [itex]\in[/itex] E
     
  2. jcsd
  3. Oct 16, 2012 #2

    LCKurtz

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    If E=(a+b)/ab what does EN* mean? What does ]0,2]E E mean? Please state your problem with proper notation.
     
  4. Oct 16, 2012 #3

    Mark44

    Staff: Mentor

    E means ##\in## and N* means the positive integers, I believe.
    I second that.
     
  5. Oct 17, 2012 #4
    well sorry didn't find the proper notations in the advanced mode umm any solution?
     
  6. Oct 17, 2012 #5

    Mark44

    Staff: Mentor

    You can use ε in the top row of Quick Symbols (on the right after you click Go Advanced). Or you can use LaTeX: [ itex ] \in [ /itex ] (without the spaces).

    Also, tell us what you meant by N*.
     
  7. Oct 17, 2012 #6

    Ray Vickson

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    You could try using words:
    E = {(a+b)/(ab): a,b positive integers}. And "is ]0,2] a subset of E?"
    or
    E = {(a+b)/(ab): a,b,in N*}, and "is ]0,2] subset E?"

    RGV
     
  8. Oct 18, 2012 #7
    I want to prove that ]0,2 is a subset of E E = {(a+b)/(ab): a,b,in N*}, and "is ]0,2] subset E?"
     
  9. Oct 18, 2012 #8

    LCKurtz

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    Aren't all the numbers in E rational?
     
  10. Oct 18, 2012 #9

    HallsofIvy

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    In other words, you want to show that if [itex]0< x\le 2[/itex], the x= (a+ b)/(ab) for some positive integers a and b. [itex]\sqrt{2}[/itex] lies between 0 and 2 doesn't it?
     
  11. Oct 19, 2012 #10
    yes it does what's your point?
     
  12. Oct 19, 2012 #11
    ohh i get your point wow that's really easy dunno how i missed it
     
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