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Math Help - Is this right?

  1. #1
    Junior Member
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    Is this right?

    Hi,

    I would like to know if I'm doing this right or wrong please help.

    For y=-2x^2, write the equation of the axis of symmetry and name the vertex.

    My answer:

    y=-2x^2

    a=(-2) , b= 0 , c= 0

    y=(-2)(0) = 0


    Then:

    x = b/2a

    x= 0/2*(-2) = (-0/4)

    So y= 0; (0,0)
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  2. #2
    MHF Contributor
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    Half of the answer is wrong.

    Vertex is (0,0), allright.

    But, axis of symmetry is not y = 0.
    Axis of symmetry is x = 0, or the y-axis.

    y = -2x^2
    It is the x that is squared, so a vertical parabola, so a vertical axis of symmetry, so x=0 or the y-axis.
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  3. #3
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    I'm sorry but I do not understand what you are telling me.
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  4. #4
    MHF Contributor
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    Which part you don't understand? All?
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  5. #5
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    This is where you lost me.

    But, axis of symmetry is not y = 0.
    Axis of symmetry is x = 0, or the y-axis.

    y = -2x^2
    It is the x that is squared, so a vertical parabola, so a vertical axis of symmetry, so x=0 or the y-axis
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  6. #6
    MHF Contributor
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    I see.

    So I assume you don't know parabolas yet.

    Funny you were told to look for the axis of symmetry of y = -2x^2, which is a vertical parabola that opens down, whose xvertex is at (0,0).

    I don't know how to proceed now.

    Wait, do you know, or can you graph y = -2x^2?
    If you can, do it. And you will see that the graph is symetrical about the y-axis. The y-axis is vertical. The y-axis is also the x=0 vertical line.
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