+73 2.) Explain how to find the coordinates of the focus of a parabola with vertex (0,0) and directrix y = 5.
+128475 The parabola opens downward because the directrix is above the vertex.....to find the focus we have
( x coordinate of the vertex, y coordinate of the vertex - y value of the directrix ) =
(0, 0 - the y value of the directrix) =
(0 , 0 - 5 ) =
(0 , - 5) = the focus
+128475 As as alternative way to do this....note that the distance between the vertex and directrix = 5 units = "p"
Since the directrix is above the vertex....the coordinates of the focus =
( x coordinate of the vertex, y coordinate of the vertex - p ) =
(0 , 0 - 5 ) =
(0, - 5)
