Results 1 to 3 of 3

Math Help - describe the domain of f(x,y,z)=ln(z-x^2-y^2+2y+3)

  1. #1
    Newbie
    Joined
    Jun 2012
    From
    canada
    Posts
    2

    describe the domain of f(x,y,z)=ln(z-x^2-y^2+2y+3)

    hi,
    the question asks for the domain of f(x,y,z)=ln(z-x^2-y^2+2y+3).

    which is z-x^2-y^2+2y+3 > 0.

    when I try do describe the domain, all I get is 2 > x^2 + (y-1)^2 -z. I have no idea what the shape is like.

    any ideas?

    thx.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor Reckoner's Avatar
    Joined
    May 2008
    From
    Baltimore, MD (USA)
    Posts
    1,024
    Thanks
    75
    Awards
    1

    Re: describe the domain of f(x,y,z)=ln(z-x^2-y^2+2y+3)

    Quote Originally Posted by sjjc1993 View Post
    hi,
    the question asks for the domain of f(x,y,z)=ln(z-x^2-y^2+2y+3).

    which is z-x^2-y^2+2y+3 > 0.

    when I try do describe the domain, all I get is 2 > x^2 + (y-1)^2 -z. I have no idea what the shape is like.
    Consider the surface

    z-x^2-y^2+2y+3=0.

    By completing the square, we have

    z+4=x^2+(y-1)^2

    This is a circular paraboloid, centered at (0,1,-4). So z+4>x^2+(y-1)^2 would consist of all the points above the paraboloid.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Jun 2012
    From
    canada
    Posts
    2

    Re: describe the domain of f(x,y,z)=ln(z-x^2-y^2+2y+3)

    thanks a lot!
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Describe A + B
    Posted in the Advanced Algebra Forum
    Replies: 11
    Last Post: October 18th 2011, 08:38 AM
  2. I dont even know how to describe it.
    Posted in the Algebra Forum
    Replies: 1
    Last Post: May 24th 2011, 05:19 AM
  3. describe this equation..
    Posted in the Calculus Forum
    Replies: 10
    Last Post: October 14th 2009, 05:56 AM
  4. Describe the locus
    Posted in the Pre-Calculus Forum
    Replies: 12
    Last Post: August 12th 2009, 08:17 PM
  5. describe S
    Posted in the Calculus Forum
    Replies: 1
    Last Post: January 15th 2007, 06:09 PM

Search Tags


/mathhelpforum @mathhelpforum