Results 1 to 4 of 4

Math Help - Inverse Functions! please help :(

  1. #1
    Newbie
    Joined
    Jan 2009
    Posts
    1

    Inverse Functions! please help :(

    f(x) = 5x + 11 / 4
    g(x) = 4x - 5 / 11

    i need to evaluate f(g(x)) and based upon the solution state wether the functions are inverse, would help gratefuly! only bit im really struggling on! wathed vids on u tube and read about 10 books but dont understand, even is someone points me in the right direction, ive tried swapping the x with a number to see if there inverse but i donth think they are, any help gratefully appreciated

    Barry
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member vincisonfire's Avatar
    Joined
    Oct 2008
    From
    Sainte-Flavie
    Posts
    469
    Thanks
    2
    Awards
    1
    In f(g(x)), g(x) acts as a variable.
    f(g(x)) = 5g(x)+\frac{11}{4}
     f(g(x)) = 5(4x-\frac{5}{11})+\frac{11}{4}
    If f(x)=g^{-1}(x) \implies g(x)=f^{-1}(x) and  f(g(x))=g(f(x))=x
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    11,621
    Thanks
    426
    Quote Originally Posted by barrypan83 View Post
    f(x) = 5x + 11 / 4
    g(x) = 4x - 5 / 11

    i need to evaluate f(g(x))
    did you mean ...

    f(x) = \frac{5x+11}{4} and g(x) = \frac{4x-5}{11} ?
    Follow Math Help Forum on Facebook and Google+

  4. #4
    MHF Contributor

    Joined
    Apr 2005
    Posts
    14,973
    Thanks
    1121
    Quote Originally Posted by barrypan83 View Post
    f(x) = 5x + 11 / 4
    g(x) = 4x - 5 / 11

    i need to evaluate f(g(x)) and based upon the solution state wether the functions are inverse, would help gratefuly! only bit im really struggling on! wathed vids on u tube and read about 10 books but dont understand, even is someone points me in the right direction, ive tried swapping the x with a number to see if there inverse but i donth think they are, any help gratefully appreciated

    Barry
    If you mean f(x)= (5x+11)/4 and g(x)= (4x- 5)/11, then f(g(x))= (5g(x)+ 11)/4= \frac{5(\frac{4x-5}{11})+ 11}{4}= \frac{\frac{20x- 25}{11}+ 11}{4}= \frac{20x- 25+ 121}{44}= \frac{20x+ 96}{44}= \frac{5x+ 24}{11}
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. inverse functions
    Posted in the Algebra Forum
    Replies: 3
    Last Post: November 22nd 2009, 04:58 PM
  2. Replies: 2
    Last Post: October 19th 2009, 02:47 AM
  3. inverse one-one functions
    Posted in the Pre-Calculus Forum
    Replies: 3
    Last Post: September 12th 2009, 04:06 PM
  4. inverse functions
    Posted in the Algebra Forum
    Replies: 2
    Last Post: April 27th 2009, 07:54 AM
  5. Functions and Inverse
    Posted in the Algebra Forum
    Replies: 2
    Last Post: April 16th 2009, 01:16 AM

Search Tags


/mathhelpforum @mathhelpforum