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Eliminating Perameter

  1. Apr 7, 2009 #1
    1. The problem statement, all variables and given/known data
    x=t^2 +t
    y=t^2-t


    2. Relevant equations
    quadratic equation


    3. The attempt at a solution
    0=t^2-t-x
    0=t^2+t+y
    [tex]
    0=\frac{-1 +- \sqrt{1+4x}}{2}
    0=\frac{1 +- \sqrt{1+4y}}{2}
    [/tex]

    Aftert i set the to quadratics equal to one another, I do not know what to do. Any help?
     
  2. jcsd
  3. Apr 7, 2009 #2

    Dick

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    The results of the quadratic equations are t, not zero. But you are still doing it the hard way. Subtract the two original equations to get an expression for t in terms of x and y. Then substitute the resulting t back into one of the equations.
     
  4. Apr 7, 2009 #3

    tiny-tim

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    Hi razored! :smile:

    Hint: go for the obvious … what is x + y? :wink:
     
  5. Apr 7, 2009 #4
    Subtracting y from x leaves me with [tex]0=x^2 -2xy+y^2-2y-2x[/tex] which is ugly. Is there anything I can do to find to y= ? No, right?

    Thank you.
     
  6. Apr 7, 2009 #5

    Dick

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    What's to do about it? You eliminated the parameter. Isn't that what they asked for? Trying to solve for y will just make it super-ugly.
     
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