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Write the equation of the quadratic function with roots -2 and 4 and a vertex at (1, 9).

  • math -

    since roots are -2 and 4,
    equation must be

    y = a(x+2)(x-4)
    but (1,9) lies on it, so
    9 = a(3)(-3)
    a = -1

    y = -1(x+2)(x-4)
    or
    y = -x^2 + 2x + 8
    or
    y = -(x-1)^2 + 9

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