Question 412786: x^2=16y i need help finding the directrix.
Answer by lwsshak3(11628)   (Show Source):
You can put this solution on YOUR website! The standard form to use is (x-h)^2=4p(y-k), with (h,k) being the (x,y) coordinates of the vertex, and p the distance from vertex to focus and vertex to directrix in the other direction on the axis of symmetry. For the given equation, x^2=16y,it is a parabola that opens upwards,the vertex is at (0,0),axis of symmetry is x=0, and 4p=16 or p=4.
The directrix, therefore, is y=-4
see the graph below:
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