Results 1 to 7 of 7

Math Help - Need help with F o G and G o F

  1. #1
    Newbie
    Joined
    Sep 2011
    Posts
    18

    Need help with F o G and G o F



    Why did I get this wrong

    I factored it to
    (4x-3)(4x-3)-2
    which gives me
    16x^2+8x-9-2
    16x^2+8x-11
    Follow Math Help Forum on Facebook and Google+

  2. #2
    Master Of Puppets
    pickslides's Avatar
    Joined
    Sep 2008
    From
    Melbourne
    Posts
    5,236
    Thanks
    29

    Re: Need help with F o G and G o F

    Your link is broken on my machine, please type the equations in case other users find the same.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    12,114
    Thanks
    992

    Re: Need help with F o G and G o F

    f(x) = x^2-2

    g(x) = 4x-3

    f[g(x)] = (4x-3)^2 - 2

    note that (4x-3)^2 \ne 16x^2+8x-9

    you need to learn how to square a binomial
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Sep 2011
    Posts
    18

    Re: Need help with F o G and G o F

    What did I do wrong?
    Follow Math Help Forum on Facebook and Google+

  5. #5
    MHF Contributor

    Joined
    Aug 2006
    Posts
    18,963
    Thanks
    1784
    Awards
    1

    Re: Need help with F o G and G o F

    Quote Originally Posted by GaDoomZ View Post


    Why did I get this wrong

    I factored it to
    (4x-3)(4x-3)-2
    which gives me
    16x^2+8x-9-2
    16x^2+8x-11
    f\circ g(x)=(4x-3)^2-2
    g\circ f(x)=4(x^2-2)-3
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor
    skeeter's Avatar
    Joined
    Jun 2008
    From
    North Texas
    Posts
    12,114
    Thanks
    992

    Re: Need help with F o G and G o F

    Quote Originally Posted by GaDoomZ View Post
    What did I do wrong?
    I told you ... you did not square the binomial (4x-3)^2 correctly.
    Follow Math Help Forum on Facebook and Google+

  7. #7
    Newbie
    Joined
    Sep 2011
    Posts
    18

    Re: Need help with F o G and G o F

    Quote Originally Posted by skeeter View Post
    I told you ... you did not square the binomial (4x-3)^2 correctly.
    Ah I see what I did wrong,

    16x^2 - 24x + 7

    thanks
    Follow Math Help Forum on Facebook and Google+


/mathhelpforum @mathhelpforum