1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Standard form of the equation of parabola

  1. Mar 25, 2009 #1
    1. The problem statement, all variables and given/known data

    Write the equation in standard form for the parabola with an axis of symmetry y=0 and focus(-5,0).

    2. Relevant equations
    I think ax^2+bx+c. Also maybe x = -b/2a. But I don't know how to apply these.

    3. The attempt at a solution
    I know that focus and vertex lie on axis of symmetry and that directrix ane axis of symmetry are perpendicular to each other.

    If you could give me a similar example worked out, I would be able to do this one. Thanks.
  2. jcsd
  3. Mar 25, 2009 #2


    Staff: Mentor

    I think not. First off, that's not an equation. Second, the axis of symmetry is the line y = 0 (the x-axis). This means that the equation will be x = ay^2 + by + c.
    x = -b/(2a) isn't the equation of a parabola; it gives you the x-coordinate of the vertex for a parabola that opens up or down. Your parabola opens left or right.
    Based on the information you provided, there are an infinite number of parabolas that satisfy these conditions. Aren't there any examples showing how to do this in your textbook?
  4. Mar 25, 2009 #3
    Hello--Thanks for responding. I cannot find an example like this one in my book. Could you give me any hints on how to begin this problem? I am completely self-taught in math and am trying to understand conics, which I have not attempted before. I am also good at following examples and, actually, learn quite a bit from them.
  5. Mar 25, 2009 #4


    Staff: Mentor

    OK, what's the example that seems the closest? Are there any examples where you're supposed to find the equation of a parabola of any kind? Maybe we can help you make some connections.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Similar Discussions: Standard form of the equation of parabola
  1. Equation of a parabola (Replies: 3)

  2. Equation of parabola (Replies: 7)