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Let f:[rr]-> [rr]

  1. Jul 13, 2003 #1
    Let f:[rr]--> [rr]

    It isn't a homework problem. :smile:
    Let f:[rr]--> [rr] be a function such that f(xy)=f(x)+f(y) for all x,y belong to real numbers
    a) Show that for all integers n, f(xn)=nf(x)
    b) Suppose the inverse of f exists. Show that for all integers n, [f-1(x)]n=f-1(nx)

    I know how to do part (a) but not part (b). Could someone please give me some hints/solution. I can't do problems involving "inverse of a function" unless they are very simple, like to find f-1 of f(x)=(1-x)/(1+x) where x does not equal to 1 or -1
     
    Last edited by a moderator: Feb 5, 2013
  2. jcsd
  3. Jul 13, 2003 #2

    Dx

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    Re: functions

    a) thats the power rule formula for solving dx
    b) this is antidx. remember its the opposite of dx. if your good with the power rule just do it backwards and subtract.

    A good toolkit for you to use.
    dx :wink:
     
  4. Jul 13, 2003 #3

    mathman

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    Gold Member

    inverse

    Let x=f(y), or y=f-1(x)
    f(yn)=nf(y)=nx
    Take inverse on both sides and get
    yn=(f-1(x))n=f-1(nx)
     
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