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Math Help - sketching level curves

  1. #1
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    sketching level curves

    Hi, I've got a level curve

    T(x,y) = 2x - y / x^2 + y^2

    at T = 0

    If i put T in i get

    0 = 2x - y / x^2 + y^2

    So what i did at first was multiply out the bottom to get

    0 = 2x - y
    y=2x

    But then i thought of inversing it first before i multiplied out so i got

    0 = x^2 + y^2 / 2x - y
    x^2 + y^2 = 0

    which one is right? am i allowed to inverse it first?

    whats goin owwwnnnn?!
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  2. #2
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    Quote Originally Posted by jarudo View Post
    Hi, I've got a level curve

    T(x,y) = 2x - y / x^2 + y^2

    at T = 0

    If i put T in i get

    0 = 2x - y / x^2 + y^2

    So what i did at first was multiply out the bottom to get

    0 = 2x - y
    y=2x Mr F says: Good.

    But then i thought of inversing it first before i multiplied out so i got Mr F thinks: Uh oh. Nothing good ever comes from a "But then I thought ...."

    0 = x^2 + y^2 / 2x - y Mr F says: Yep, I was right.

    This is utter rubbish. How can you possibly take the reciprocal of the left hand side of 0 = 2x - y / x^2 + y^2 and get zero!!! You should know better - isn't this a 2nd year university level mathematics subject you're enrolled in.


    x^2 + y^2 = 0

    which one is right? am i allowed to inverse it first?

    whats goin owwwnnnn?!
    This particular assignment question is sure turning up some interesting thinking.
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  3. #3
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    haha thanks mr f
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