Results 1 to 4 of 4

Math Help - Domain and range - functions and relations :D

  1. #1
    Junior Member
    Joined
    Mar 2008
    Posts
    30

    Domain and range - functions and relations :D

    Hello all!

    We're currently learning about Functions and Relations. Here is a question im unsure about. Help would be greatly appreciated.

    Question: For the following function, state:

    (i) the domain
    (ii) the co-domain
    (iii) the range
    f : ( - , 0 ) R , f (x) = 1/ - x (one divided by square root of negative x)

    I'm more concerned about how to do the range... because the answer says that the range is: ( 0 , ). How do you know with those types of graphs ( sqaure root underneath ) what the range is?

    Help would be greatly appreciated! Thank- you
    Last edited by steph_r; May 21st 2008 at 12:29 AM. Reason: mistake
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,830
    Thanks
    123
    Quote Originally Posted by steph_r View Post
    Hello all!

    We're currently learning about Functions and Relations. Here is a question im unsure about. Help would be greatly appreciated.

    Question: For the following function, state:

    (i) the domain
    (ii) the co-domain
    (iii) the range

    f : ( - , 0 ) R , f (x) = 1/ - x (one divided by square root of negative x)

    I'm more concerned about how to do the range... because the answer says that the range is: ( 0 , ). How do you know with those types of graphs ( sqaure root underneath ) what the range is?

    Help would be greatly appreciated! Thank- you
    If you have

    f(x)=\frac1{\sqrt{-x}}

    Then you have to consider: 1. the radical must be greater or equal zero and 2. the denominator must be unequal zero.

    to 1.: -x\geq 0~\implies~ x \leq 0

    to 2.: x \ne 0

    therefore the domain of your function is x \in (-\infty, 0)

    Since \sqrt{-x} > 0 the range of the function are all positive numbers:

    y \in (0, +\infty)
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Junior Member
    Joined
    Mar 2008
    Posts
    30

    Functions

    So.. does the line of that equation, when graphed on the calculator, actually touch the y-intercept? because im unsure about why the is there .

    Thank you
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Super Member
    earboth's Avatar
    Joined
    Jan 2006
    From
    Germany
    Posts
    5,830
    Thanks
    123
    Quote Originally Posted by steph_r View Post
    So.. does the line of that equation, when graphed on the calculator, actually touch the y-intercept? because im unsure about why the is there .

    Thank you
    As I've posted in my previous post zero doesn't belong to the range. To illustrate the behaviour(?) of the function I've attached the graph of f:
    Attached Thumbnails Attached Thumbnails Domain and range  - functions and relations :D-gebr_wurzelneg.jpg  
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Range and Domain of Functions
    Posted in the Calculus Forum
    Replies: 1
    Last Post: March 5th 2011, 12:49 PM
  2. domain & range of functions
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: September 24th 2010, 08:25 AM
  3. Domain and Range Functions
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: June 4th 2009, 11:43 PM
  4. Domain and Range Functions
    Posted in the Calculus Forum
    Replies: 4
    Last Post: June 4th 2008, 05:35 PM
  5. Functions, Domain & Range
    Posted in the Discrete Math Forum
    Replies: 2
    Last Post: April 30th 2008, 09:24 AM

Search Tags


/mathhelpforum @mathhelpforum