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Math Help - Determine the quadratic function whose graph is given

  1. #1
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    Determine the quadratic function whose graph is given

    Hi All,

    I would really appreciate some help/hints for the following problem I am stuck on.
    Determine the quadratic function whose graph is given:
    The function has given points at (-1,5), (3,5), and y-intercept at (0,-1)

    I know that the axis of symmetry (h) is at 1 because it is the mid-point between -1 and 3. If I plug that into the function a(x-h)^2 + k, I still have two unknowns, a and k
    a(x-1)^2+k
    Can someone please explain to me how to solve this. Thank you very much in advance.

    Alex
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: Determine the quadratic function whose graph is given

    Let:

    f(x)=ax^2+bx+c and use the given points to state:

    f(-1)=5

    f(0)=-1

    f(3)=5

    The second equation tells you c=-1, and this along with the first and third equations will give you two equations and two unknowns.
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