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Math Help - conics

  1. #1
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    2 math questions:p

    Which equation describes a circle?
    A: -2y2+y+2x2-5x-3=0
    B: -3x2+x-6y2+y=4
    C: -3y2+x+y=3

    Identify the conic section with the given equation 5x2-6y2-9x+2y+3=0

    p.s. the twos are supposed to be raised to that power
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  2. #2
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    None of those is a circle. In a general quadratic form, if the coefficients of x^2 and y^2 are equal, it's a circle; unequal but the same sign, an ellipse; one zero and one non-zero, a parabola; of different sign, a hyperbola (rectagular if the coefficients are equal in absolute value). So you have a rectangular hyperbola, an ellipse and a parabola respectively.
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  3. #3
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    Quote Originally Posted by Lane
    ...
    Identify the conic section with the given equation 5x2-6y2-9x+2y+3=0
    ...
    Hello, Lane,

    as rgep explained this equation describes a hyperbola.

    Greetings

    EB
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  4. #4
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    The quadradic in form of,
    <br />
ax^2+2hxy+by^2+2gx+2fy+c=0
    can de determined by looking a the relationship between,
    h^2 and ab.

    h^2=ab---->parabola
    h^2>ab---->hyperbola
    h^2<ab---->ellipse
    In your case we have #2 which is a hyperbola.

    [Note: Some cases where not considered such as the coditions for a general quadradic to represent a line or to represent a point]
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