Question 812895
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Hi

endpoints of the latus rectum of a parabola are (5,k), and (-5,k).
vertex of the parabola is at the origin, and the parabola opens downward
the vertex form of a Parabola opening up(a>0) or down(a<0), {{{y=a(x-h)^2 +k}}} 
where(h,k) is the vertex  and  x = h  is the Line of Symmetry
The standard form is {{{(x -h)^2 = 4p(y -k)}}}, where  the focus is (h,k + p)
{{{(x -0)^2 = 4p(y -0)}}},  
4p = 10, (length of latus rectum is 4p   Focal point is ( 0,-10/4 )  
{{{-x^2 = 10y}}}
{{{drawing(300,300,   -10,10,-10,10,  
 grid(1),
circle(-5, -2.5,0.4),
circle(5, -2.5,0.4),
circle(0, -2.5,0.4),
graph( 300, 300, -10,10,-10,10,0, (-1/10)x^2))}}}