Results 1 to 4 of 4

Math Help - discrete function - onto and 1-1

  1. #1
    Newbie
    Joined
    Oct 2008
    Posts
    13

    discrete function - onto and 1-1

    Give a example of a function from N to N (naturals) that is
    a) one-to-one and onto
    b) onto but not one-to-one
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,605
    Thanks
    1574
    Awards
    1
    What about f(n) = \left\lfloor {\frac{n}{2}} \right\rfloor ?
    Which part does that answer?
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor

    Joined
    Apr 2005
    Posts
    15,405
    Thanks
    1328
    Quote Originally Posted by pila0688 View Post
    Give a example of a function from N to N (naturals) that is
    a) one-to-one and ontoo
    An obvious answer: f(n)= n.

    b) onto but not one-to-one
    Try mapping each even number, 2n, into n and each odd number, 2n+ 1 into n.

    That is, 1->1, 2->1, 3->2, 4->2, etc.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    Mar 2007
    Posts
    33
    Would f(n) = n^2 be onto but not 1-1?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. discrete function help
    Posted in the Statistics Forum
    Replies: 2
    Last Post: December 7th 2010, 09:01 PM
  2. discrete math function
    Posted in the Discrete Math Forum
    Replies: 2
    Last Post: September 26th 2010, 02:36 PM
  3. Asymptotic expansion of a discrete function
    Posted in the Differential Geometry Forum
    Replies: 11
    Last Post: February 21st 2010, 12:48 PM
  4. Discrete Geometric Moment Generating Function
    Posted in the Advanced Statistics Forum
    Replies: 3
    Last Post: November 8th 2009, 04:38 AM
  5. discrete probability density function!
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: October 17th 2008, 07:30 AM

Search Tags


/mathhelpforum @mathhelpforum