Question 316878
The equation is already in vertex form,
{{{y=(1/12)(x-0)^2+0}}}
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The vertex is (0,0).
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The general equation for a parabola is,
{{{4p(y-k)=(x-h)^2}}} where p is the distance from the vertex to the focus. 
In your case,
{{{12(y-0)=(x-0)^2}}}
{{{4p=12}}}
{{{p=3}}}
The focus is located at (0,0)+(0,3)=(0,3)
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The directrix is the same distance from the vertex but in the opposite direction.
{{{y=-3}}}
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{{{drawing(300,300,-6,6,-6,6,grid(1),circle(0,0,.3),circle(0,3,.3),blue(line(-10,-3,10,-3)),graph(300,300,-6,6,-6,6,(1/12)x^2))}}}