document.write( "Question 615730: Write the equation of a parabola that has a focus pointlocated at (-3,-1) and the equation of the directrix is y=3. \n" ); document.write( "

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Write the equation of a parabola that has a focus pointlocated at (-3,-1) and the equation of the directrix is y=3.
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\n" ); document.write( "Given parabola opens downwards:
\n" ); document.write( "Its standard form of equation: (x-h)^2=-4p(y-k), (h,k)=(x,y) coordinates of vertex
\n" ); document.write( "For given parabola:
\n" ); document.write( "x-coordinate of vertex=-3 (fm given focus coordinates)
\n" ); document.write( "y-coordinate of vertex=1 (halfway between focus and directrix on axis of symmetry, x=-3)
\n" ); document.write( "vertex: (-3,1)
\n" ); document.write( "p=2 (distance from directrix or focus to vertex on axis of symmetry)
\n" ); document.write( "4p=8
\n" ); document.write( "Equation of given parabola:
\n" ); document.write( "(x+3)^2=-8(y-1)
\n" ); document.write( "see graph below as a visual check:
\n" ); document.write( "y=-(x+3)^2/8+1
\n" ); document.write( " $\"+graph%28+300%2C+300%2C+-10%2C+10%2C+-10%2C+10%2C-%28x%2B3%29%5E2%2F8%2B1%29+\"$
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