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Math Help - Precal: finding formula for quadratic function

  1. #1
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    Precal: finding formula for quadratic function

    Find a formula for the quadratic function whose graph has the given properties:

    A y-intercept of y = 7 and x-intercepts at x = 1, 4


    Help please! i don't know how to find the formula...
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  2. #2
    MHF Contributor
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    Write down an arbitrary quadratic function:

    For Example:
    y = a(x-b)(x-c)

    Fill in the details:

    "x-intercepts at x = 1, 4"

    y = a(x-1)(x-4)

    You do the y-intercept.
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  3. #3
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    it wouldn't be y = (1-b)(4-c) because they're x's?
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  4. #4
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by sksksk View Post
    it wouldn't be y = (1-b)(4-c) because they're x's?
    TKHunny is telling you the general form of a quadratic function:
    y = a(x - b)(x - c)
    where b and c are the two zeros of the quadratic.

    You are applying this to your specific problem where b = 1 and c = 4.

    -Dan
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  5. #5
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    ohh... got it. thanks
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