Question 976504: Find the equation of the parabolaparabola with a focus of (-1,-3) and directrix of y:-1. Please explain step by step. I have a test andand I don't understand.
Answer by stanbon(75887)   (Show Source):
You can put this solution on YOUR website! Find the equation of the parabolaparabola with a focus of (-1,-3) and directrix of y = -1. Please explain step by step. I have a test andand I don't understand.
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Plot the focus (-1,-3)
Draw the directrix:: y = -1
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Note that the directrix is above the focus
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The vertex is half-way between the focus
and the directrix.
Vertex:: (-1,-2)
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p is the distance from vertex to the focus::
p = -1
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Form:: (x-h) = 4p(y-k)
(x+1)^2 = -4(y+2)
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y+2 = (-1/4)(x^2 + 2x + 1)
y = (-1/4)x^2 - (1/2)x - (9/4)
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Cheers,
Stan H.
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