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Math Help - True or False traces of functions

  1. #1
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    True or False traces of functions

    True of False
    The trace of x^2+2y^2 +10z^2=5 in the plane z=2 is an ellipse. True or False?

    False because x^2+2y^2=-35 is not an ellipse. But what is it if it is not any ellipse?
    Last edited by andreaspohle; November 1st 2009 at 11:46 AM.
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  2. #2
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    Quote Originally Posted by andreaspohle View Post
    True of False
    The trace of x^2+2y^2 +10z^2=5 in the plane z=2 is an ellipse.

    False because x^2+2y^2=-35 is an ellipse, so true is that correct?

    Please do read the last line you wrote above and tell me if you really expect anyone but yourself to understand it: what are you asking there?? Is like the following:

    Claim: A is B
    Answer: False because A is B, so true is that correct?

    Does this make any sense to you?

    Btw, the answer is, of course, false, since sum of squares and positives cannot be a negative number

    Tonio
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  3. #3
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    Sorry for that. I fixed it, thank you.
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