Write the equation in vertex form for the parabola with focus \( (0,-7) \) and directrix \( y=9 \) Simplify any fractions. \( \begin{array}{lll}\text { Submit }\end{array} \)
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To find the vertex form of the parabola with focus \( (0,-7) \) and directrix \( y=9 \), we start by determining the vertex. The vertex is located halfway between the focus and the directrix, so we calculate the midpoint: \[ \text{Vertex } V = \left(0, \frac{-7 + 9}{2}\right) = \left(0, 1\right). \] The distance \( p \) from the vertex to the focus (or directrix) is: \[ p = -7 - 1 = -8 \quad \text{(since it's opening downward)}. \] The vertex form of a parabola that opens downward is given by: \[ y = a(x-h)^2 + k, \] where \( (h, k) \) is the vertex and \( a = \frac{1}{4p} \). Plugging in the values we have: \[ a = \frac{1}{4(-8)} = -\frac{1}{32}. \] Thus, the equation in vertex form is: \[ y = -\frac{1}{32}(x-0)^2 + 1. \] Finally, the equation simplifies to: \[ y = -\frac{1}{32}x^2 + 1. \] Now you've got the vertex form of the parabola!