Results 1 to 5 of 5

Math Help - Inverse of an absolute value

  1. #1
    Member
    Joined
    Jun 2008
    Posts
    88

    Inverse of an absolute value

    I've whittled it down to:
    y = (e^x+1)/2
    and y = (-e^x-1)/2
    For positive and negative takes on the absolute value, but which do I choose?
    What's more, as it says "state the rule", should I present my answer as f^-1-infinity,a), etc? Presenting the entire rule like they do in the question?

    Oh, and also, in the previous question we worked out a = 1/2.
    Attached Thumbnails Attached Thumbnails Inverse of an absolute value-11-09-2008-12-48-46pm.jpg  
    Follow Math Help Forum on Facebook and Google+

  2. #2
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by Naur View Post
    I've whittled it down to:
    y = (e^x+1)/2
    and y = (-e^x+1)/2
    For positive and negative takes on the absolute value, but which do I choose?
    What's more, as it says "state the rule", should I present my answer as f^-1-infinity,a), etc? Presenting the entire rule like they do in the question?

    Oh, and also, in the previous question we worked out a = 1/2.
    i suppose the base is "e", i couldn't see it that well.

    anyway, take both. you can define a piece-wise function
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Member
    Joined
    Jun 2008
    Posts
    88
    Oh yes, the base is e. My mistake.
    And you're right, that's a mistake, should be a positive.

    Here's the answer as it's given. They have a way of defining which one to use. I guess it kind of makes sense, when y is negative it's on the negative side of the y-axis, which fits the domain, so it must be that one.
    Is that it though?
    It can be hard to accurately judge the rule they've used when all they show is the maths involved.
    Attached Thumbnails Attached Thumbnails Inverse of an absolute value-answer.jpg  
    Follow Math Help Forum on Facebook and Google+

  4. #4
    is up to his old tricks again! Jhevon's Avatar
    Joined
    Feb 2007
    From
    New York, USA
    Posts
    11,663
    Thanks
    3
    Quote Originally Posted by Naur View Post
    Oh yes, the base is e. My mistake.
    And you're right, that's a mistake, should be a positive.

    Here's the answer as it's given. They have a way of defining which one to use. I guess it kind of makes sense, when y is negative it's on the negative side of the y-axis, which fits the domain, so it must be that one.
    Is that it though?
    It can be hard to accurately judge the rule they've used when all they show is the maths involved.
    ok, they gave you a range. yes, then that answer is correct. you have to make sure the domains match up. since x < 1/2 for the function, you need y < 1/2 for the inverse function
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Member
    Joined
    Jun 2008
    Posts
    88
    Ah okay. I'll try to remember that, thanks very much
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Inverse of an absolute function
    Posted in the Algebra Forum
    Replies: 3
    Last Post: October 3rd 2011, 05:20 PM
  2. Absolute value inverse.
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: August 24th 2010, 02:19 AM
  3. Replies: 2
    Last Post: November 8th 2009, 01:52 PM
  4. Finding inverse of absolute function
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: September 25th 2009, 10:22 PM
  5. Inverse of absolute value
    Posted in the Pre-Calculus Forum
    Replies: 7
    Last Post: October 9th 2008, 05:30 PM

Search Tags


/mathhelpforum @mathhelpforum