Q. Write the equation in vertex form for the parabola with focus (7,415) and directrix y=−415.
Identify Parabola Orientation: Identify whether the parabola is vertical or horizontal.Since the directrix is a horizontal line y=constant, the parabola is vertical.
Vertex Form of Vertical Parabola: Identify the vertex form of a vertical parabola.The vertex form of a vertical parabola is y=a(x−h)2+k, where (h,k) is the vertex.
Determine Vertex: Determine the vertex of the parabola.The vertex lies midway between the focus and the directrix. Since the focus is at (7,415) and the directrix is y=−(415), the y-coordinate of the vertex will be the average of 415 and −415, which is 0. The x-coordinate of the vertex is the same as the x-coordinate of the focus, which is 7. Therefore, the vertex is at (7,0).
Determine Parabola Direction: Determine if the parabola opens upward or downward.The focus is above the directrix, so the parabola opens upward.
Calculate Value of 'a': Calculate the value of 'a'.The distance between the vertex and the focus (or directrix) is the absolute value of the difference in their y-coordinates. This distance is also equal to 4a1. The distance between the focus and the directrix is 415−(−415)=215. Therefore, 4a1=215, and a=4×2151=301.
Write Parabola Equation: Write the equation of the parabola.Substitute a=301, h=7, and k=0 into the vertex form equation.y=(301)(x−7)2+0y=(301)(x−7)2
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