+1993 Which equation represents a parabola that has a focus of (0, 0) and a directrix of y = 4?
x^2=−8y
x^2=−8(y−2)
x^2=−2(y−2)
x^2=−2y
+128407 If the directri is y = 4 and the focus is (0,0).....the vertex = (0, (0 + 4)/2 ) = (0, 2 )= (h, k)
In other words....the vertex is midway between the focus and the directrix
p is the distance between the vertex and the focus = 2
And since the directrix is above the focus, the parabola opens downward
And we have the form
-4p ( y - k) = x^2
-4p(y-2) = x^2 (we use the " - " because the parabola opens downward )
- 4(2) (y -2) = x^2
-8(y - 2) = x^2
EDIT TO CORRECT AN ERROR
