Results 1 to 5 of 5

Math Help - Find The forumula for the inverse of a given function

  1. #1
    Newbie
    Joined
    Jan 2011
    Posts
    13
    Thanks
    1

    Find The forumula for the inverse of a given function

    So one problem is f(x)=x^3 , In my head I know its x^(1/3) because
    y=x^3
    Then i think I Do the third square root to both sides to get that answer but am not sure.

    This is the one where Im haveing the most trouble

    f(x)=(3x+1)/(2x-5) So I Multipy each side by 2x-5 and get
    y(2x-5) which factors into
    2xy-5y=3x+1 and am not sure what to do from here

    Any help would be greatly appreciated.

    The answer in the back of the book is y=(5x+1)/(2x-3)
    even with that I cant figure out how they came up with it
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Senior Member
    Joined
    Feb 2013
    From
    Saudi Arabia
    Posts
    443
    Thanks
    86

    Re: Find The forumula for the inverse of a given function

    transfer all terms with y to the right side and all x to the left and solve for x ...to be a function of y..the interchange the x with y and thats it...you must find
    (5x+1)/(2x-3) as inverse to the original function

    Good luck
    Minoas
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Newbie
    Joined
    Nov 2012
    From
    PA
    Posts
    21
    Thanks
    1

    Re: Find The forumula for the inverse of a given function

    I can help you to a certain extent, but the ONLY thing I myself am unsure of is why it's 5x+1 and not 5x-1, or -5x+1 conversely.

    First, the easiest way to solve this would be to switch the x's and y's. Equation becomes

    x=\frac{3y+1}{2y+5}.

    You were correct to multiply the denominator, then you get

    x(2y+5)=3y+1.

    Distribute:

    2xy+5x=3y+1

    Isolate all terms with y on one side, so I'll subtract 3y from the right and 5x from the left to keep the formatting of your books answer more intact:

    2xy-3y=-5x+1

    Factor out a y

    y(2x-3)=-5x+1 and divide by 2x-3

    y=(-5x+1)/(2x-3)


    Now you just have to hope that either your book is wrong or somebody can explain to you why it's 5x+1 without a negative.

    Hope I helped at least a bit.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Jan 2011
    Posts
    13
    Thanks
    1

    Re: Find The forumula for the inverse of a given function

    It started out as f(x)=(3x+1)/(2x-5) I think you did f(x)=(3x+1)/(2x+5)

    Thank you though i just couldn't wrap my head around it.
    I Was failing at getting like terms on their own side I think.
    I went through it again and got the correct Answer TYVM

    Also where is the reference material for this site to make my math problems look like yours
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Nov 2012
    From
    PA
    Posts
    21
    Thanks
    1

    Re: Find The forumula for the inverse of a given function

    Oops, 2x-5 would indeed make a ton more sense as to why it's 5x+1 lol. Not sure why my mind read it as 2x+5.

    And the way to format math problems like this is called LaTex, there's a specific sub-forum on this website with how to do it all. Everything goes inside [ tex][/tex] brackets.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Find the inverse. Is it a function
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: May 29th 2012, 03:16 PM
  2. Replies: 1
    Last Post: March 5th 2012, 12:41 AM
  3. find inverse function
    Posted in the Algebra Forum
    Replies: 3
    Last Post: October 13th 2009, 09:08 AM
  4. Help me find the inverse of this function!
    Posted in the Algebra Forum
    Replies: 8
    Last Post: September 20th 2008, 04:27 PM
  5. help me to find the inverse function
    Posted in the Calculus Forum
    Replies: 2
    Last Post: August 25th 2006, 12:38 PM

Search Tags


/mathhelpforum @mathhelpforum