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Handling a Fraction

  1. Feb 13, 2013 #1
    I'm trying to figure out how to calculate the velocity of an orbit at apogee or perigee and I've figured out the derivation of the equation except for this one fraction... I replaced the radius quantities for x and y for ease of viewing.

    [itex]\frac{x-y}{x^2 - y^2} = \frac{1}{x + y}[/itex]

    Can anybody break this down for me barney-style?
     
  2. jcsd
  3. Feb 13, 2013 #2

    trollcast

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    Gold Member

    Express the $$x^2-y^2$$ as the difference of 2 squares.

    Then it will cancel to give the right hand fraction.
     
  4. Feb 13, 2013 #3

    HallsofIvy

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    Science Advisor

    As long as x- y is not equal to 0, [itex](x^2- y^2)/(x- y)= (x- y)(x+ y)/(x- y)= x+ y[/itex].
     
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