Question 81488
write an equation for parabola  
   focus (3,8),directrix y=4
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Draw the line y=4.
Plot the point (3,8)
The focus is above the directrix and is 2p away from it.
So 2p=4; p=2
The vertex is half way between the focus and the directrix.
So the vertex is (3,6)
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EQUATION:
4p(y-k)=(x-h)^2
8(y-6)=(x-3)^2
8y-48=x^2-6x+9
8y=x^2-6x+57
y=(1/8)x^2-(3/4)x+57/8
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Cheers,
Stan H.