Question 585288
find the equation of parabola whose vertex at origin and directrix x=2
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Standard form of equation for a parabola that opens leftwards(directrix is to the right of the vertex): 
(y-k)^2=-4p(x-h), (h,k) being the (x,y) coordinates of the vertex. 
For given parabola:
vertex:(0,0)
axis of symmetry: x-axis or y=0
p=2 (distance from vertex to directrix on the axis of symmetry)
equation of given parabola:
y^2=-4px
y^2=-8x