Results 1 to 2 of 2

Math Help - Parabola question

  1. #1
    Junior Member
    Joined
    Jan 2010
    Posts
    25

    Parabola question

    Given
    x^2-4x=y+4
    Find the vertex, focus and directrix

    So i know that i need to complete the square
    x^2-4x+4=y+4+4

    (x-2)^2=(y+8)

    Vertex is at (2,-8)

    and im having a bit of trouble on the focus and directrix....

    Thanks
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Junior Member
    Joined
    Jan 2010
    Posts
    25
    okay i figured it out...

    (x-2)^2=a(y+8)
    Since (y+8) doesn't factor, then
    a=1
    general form is x^2=4ay
    set 4a=1 => a=1/4

    directrix @ y=-8.25
    focus @ (2,-7.75)

    gotta love when posting on here rings a bell.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Parabola Question
    Posted in the Algebra Forum
    Replies: 2
    Last Post: November 16th 2010, 05:40 AM
  2. Parabola question
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: June 6th 2010, 01:45 PM
  3. parabola question
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: May 26th 2009, 09:44 PM
  4. Parabola Question
    Posted in the Geometry Forum
    Replies: 3
    Last Post: May 5th 2009, 10:23 AM
  5. parabola question
    Posted in the Algebra Forum
    Replies: 1
    Last Post: March 28th 2009, 07:42 PM

Search Tags


/mathhelpforum @mathhelpforum