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Thread: Getting the standard form of ellipse.

  1. #1
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    Getting the standard form of ellipse.

    Hey guys,
    How do I convert this equation:

    4x^2 -4x +8y^2 +48y = -57
    into the standard form of an ellipse's formula.

    I know that the right hand side has to be 1 but O don't know what to do with the first degree x and y terms.
    Last edited by mr fantastic; Jun 25th 2011 at 03:26 PM. Reason: Re-titled.
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  2. #2
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    Re: Circle formula

    Quote Originally Posted by elieh View Post
    4x^2 -4x +8y^2 +48y = -57
    into the standard form of an ellipse's formula.
    I'll get you started.
    4x^2 -4x +8y^2 +48y=4(x-0.5)^2+8(y+3)^2-1-72 .

    You should expand that to check my work.
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  3. #3
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    Re: Circle formula

    Got it!

     \frac{(x-0.5)^2}{4} + \frac{(y+3)^2}{2} =1
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  4. #4
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    Re: Circle formula

    In other words, complete the square.
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  5. #5
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    Re: Circle formula

    You'll find that whenever you want a circle or ellipse, completing the square is required.
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