Results 1 to 6 of 6

Math Help - How to solve the function fg(2x)

  1. #1
    Junior Member
    Joined
    Oct 2011
    Posts
    37

    How to solve the function fg(2x)

    I've become a bit confused on a question that is:

    let f(x)=x^2-1 and g(x)=2x+1

    Calculate fg(2x)


    I'm not too sure. Is it:

    f(2(2x)+1) or f(2(2x+1))?

    Thanks very much!
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Junior Member Kanwar245's Avatar
    Joined
    Jun 2011
    From
    Canada
    Posts
    68
    Thanks
    2

    Re: How to solve the function fg(2x)

    I think fg should be 2x^3 + x^2 - 2x - 1 and then you just plug in 2x in place of x to get your ans.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    Senior Member
    Joined
    Nov 2011
    From
    Crna Gora
    Posts
    420
    Thanks
    64

    Re: How to solve the function fg(2x)

    Quote Originally Posted by BobtheBob View Post
    I've become a bit confused on a question that is:

    let f(x)=x^2-1 and g(x)=2x+1

    Calculate fg(2x)


    I'm not too sure. Is it:

    f(2(2x)+1) or f(2(2x+1))?

    Thanks very much!
    (f \circ g)(x)=(2x+1)^2-1=4x^2+4x

    (f \circ g) (2x)=4(2x)^2+4\cdot 2x=16x^2+8x
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Junior Member
    Joined
    Oct 2011
    Posts
    37

    Re: How to solve the function fg(2x)

    Ok thanks very much for the help! Much appreciated.
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Junior Member Kanwar245's Avatar
    Joined
    Jun 2011
    From
    Canada
    Posts
    68
    Thanks
    2

    Re: How to solve the function fg(2x)

    Quote Originally Posted by princeps View Post
    (f \circ g)(x)=(2x+1)^2-1=4x^2+4x

    (f \circ g) (2x)=4(2x)^2+4\cdot 2x=16x^2+8x
    I think that is the wrong way of doing it. it's not fog
    Follow Math Help Forum on Facebook and Google+

  6. #6
    Junior Member
    Joined
    Oct 2011
    Posts
    37

    Re: How to solve the function fg(2x)

    Oh right. I originaly got 16x^2 + 8x though although I wasn't sure of it...?
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. How to solve this function
    Posted in the Algebra Forum
    Replies: 3
    Last Post: October 4th 2011, 02:46 PM
  2. Solve the function
    Posted in the Pre-Calculus Forum
    Replies: 4
    Last Post: August 31st 2010, 08:23 PM
  3. how to solve this function for a and b
    Posted in the Calculus Forum
    Replies: 2
    Last Post: February 15th 2009, 03:36 PM
  4. Solve for y as a function of x
    Posted in the Calculus Forum
    Replies: 3
    Last Post: December 7th 2007, 01:12 PM
  5. How to solve function
    Posted in the Calculus Forum
    Replies: 1
    Last Post: April 4th 2006, 07:32 AM

Search Tags


/mathhelpforum @mathhelpforum