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Rational Expression

  1. May 8, 2008 #1
    1. The problem statement, all variables and given/known data

    I have volunteered to help a friend's son with his Algebra 2 (thinking - no problem, I've had Calc 1-3, differential equation, complex variables, probability / stats and so on.

    So I start to help and the first questions:

    Why aren't these rational expressions:
    [tex]
    \frac {\sqrt(x)}{(x+3)}
    [/tex]

    and


    [tex]
    \frac {\sqrt{(x-y)^2}}{(x)}
    [/tex]



    2. Relevant equations



    3. The attempt at a solution


    I know if the square root wasn't in the numerator they would be rational - at least I hope I'm correct.

    I don't know why they aren't reational.

    Thanks
    -Sparky
     
  2. jcsd
  3. May 8, 2008 #2

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Yes, a "rational function" is defined as "a polynomial divided by a polynomial". What you give is not a rational function because [itex]\sqrt{x}[/itex] is not a polynomial.
     
  4. May 8, 2008 #3
    Ok - "polynomial divided by polynomial"

    I was going to have to dig out my old algebra book. - in fact I probably still will have to dig it out to avoid embarassment.

    Thanks so much!!!!
     
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