Q. Write the equation in vertex form for the parabola with vertex (0,−7) and directrix y=−4.Simplify any fractions.______
Identify orientation: Identify the orientation of the parabola.Since the directrix is horizontal y=−4, the parabola is vertical.
Determine opening direction: Determine the direction the parabola opens.The vertex (0,−7) is below the directrix y=−4, so the parabola opens upward.
Calculate distance to directrix: Calculate the distance between the vertex and the directrix.Distance = ∣−7−(−4)∣=∣−7+4∣=∣−3∣=3
Find value of a: Find the value of a using the distance.The distance is equal to 4a1, so 3=4a1.Solve for a: a=4×31=121.
Write equation in vertex form: Write the equation in vertex form.Vertex form for a vertical parabola is y=a(x−h)2+k.Substitute a=121, h=0, and k=−7.y=121(x−0)2−7y=121x2−7
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