Thursday, October 17, 2013

(0,7/4) Write the standard form of the equation of the parabola with the given focus and vertex at (0,0)

A parabola opens toward to the location of focus with respect to the vertex.
When the vertex and focus has same y-values, it implies that the parabola opens sideways (left or right). 
When the vertex and focus has same x-values, it implies that the parabola may opens upward or downward. 
The given focus of the parabola (0, 7/4) is located above the vertex (0,0) . Both points has the same value of x=0 .
Thus, the parabola opens upward. In this case, we follow the standard formula: (x-h)^2=4p(y-k) . We consider the following properties:
 vertex as (h,k)
 focus as (h, k+p)
  directrix as y=k-p
 Note: p is the distance of between focus and vertex or distance between directrix and vertex.
From the given vertex point (0,0) , we determine h =0 and k=0.
From the given focus (0,7/4) , we determine h =0 and k+p=7/4 .
Plug-in  k=0 on k+p=7/4 . we get:
0+p=7/4
p=7/4
Plug-in the values: h=0 ,k=0 , and p=7/4  on the standard formula, we get:
(x-0)^2=4*7/4(y-0)
x^2=7y  as the standard form of the equation of the parabola with vertex (0,0) and focus (0,7/4) .

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