Results 1 to 3 of 3

Thread: functions

  1. #1
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,237
    Thanks
    33

    [SOLVED] functions

    The function $\displaystyle f$ has the property that $\displaystyle f(x)+f(y)= (x+y)f(xy)$ for all non-zero real numbers $\displaystyle x$ and $\displaystyle y$ . A possible rule for $\displaystyle f $ is

    A. $\displaystyle f(x)=2x$

    B. $\displaystyle f(x)=5-2x$

    C. $\displaystyle f(x) = \frac{1}{x}$

    D. $\displaystyle f(x)= e^x$

    E. $\displaystyle f(x)=\ln x$

    I can expand every option out. But I'm having a lazy day. Is there an easier way?
    Last edited by pickslides; Apr 7th 2010 at 05:11 PM.
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,237
    Thanks
    33
    C. is the answer. Just lazy I am.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Super Member Bacterius's Avatar
    Joined
    Nov 2009
    From
    Wellington
    Posts
    927
    I don't think so. I've been thinking but I can't express the property in natural terms that do not require expanding each function to see if it matches.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Replies: 0
    Last Post: Apr 15th 2010, 05:50 PM
  2. Replies: 3
    Last Post: Feb 23rd 2010, 04:54 PM
  3. Replies: 11
    Last Post: Nov 15th 2009, 11:22 AM
  4. Replies: 7
    Last Post: Aug 12th 2009, 04:41 PM
  5. Replies: 1
    Last Post: Apr 15th 2008, 09:00 AM

Search Tags


/mathhelpforum @mathhelpforum