## Directrix and Focus

vertex (-2, 3), focus (0,3)

Find the equation of the parabola.

Dirac.
 PhysOrg.com science news on PhysOrg.com >> King Richard III found in 'untidy lozenge-shaped grave'>> Google Drive sports new view and scan enhancements>> Researcher admits mistakes in stem cell study

Recognitions:
Homework Help
 Quote by Dirac vertex (-2, 3), focus (0,3) Find the equation of the parabola. Dirac.
What have you tried so far?
Find the directix. then recall
A parabola is the set of point equidistant from the focus and directix.

 Quote by lurflurf What have you tried so far? Find the directix. then recall A parabola is the set of point equidistant from the focus and directix.
So far I have got to this

((y-3)^2)=4a(x+2)

What now

Dirac.

Recognitions:
Homework Help

## Directrix and Focus

 Quote by Dirac So far I have got to this ((y-3)^2)=4a(x+2) What now Dirac.
a will be the distance between the focus and vertex.
Why is this?

 Quote by lurflurf a will be the distance between the focus and vertex. Why is this?
How does one find the vertex

Recognitions:
Homework Help
 Quote by Dirac How does one find the vertex
you started out with
vertex (-2, 3), focus (0,3)
The points of a parabola are equidistant from it directrix and focus.
The vertex is the point closest to them. that is
distance(vertex,focus)<=distance(point on parabola,focus)
with equality only when the point is the vertex.

 Quote by lurflurf you started out with vertex (-2, 3), focus (0,3) The points of a parabola are equidistant from it directrix and focus. The vertex is the point closest to them. that is distance(vertex,focus)<=distance(point on parabola,focus) with equality only when the point is the vertex.
Could you just post the answer, or would it get up your backside to post something useful in your life

Dirac.

Recognitions:
Homework Help
 Quote by Dirac Could you just post the answer, or would it get up your backside to post something useful in your life Dirac.
I already said you a is the distance between
vertex (-2, 3), focus (0,3)
here you go
a=sqrt[(0-(-2))^2+(3-3)]
=sqrt[2^2]
a=2
Do you understand why?
Can you find the equation of a parabola with
vertex (0,0), focus (0,-4)

Recognitions:
Gold Member