Results 1 to 2 of 2

Thread: Composition of Two Functions

  1. #1
    Member
    Joined
    Nov 2007
    Posts
    232

    Composition of Two Functions

    Given $\displaystyle f(x) = -5x + 2$ and $\displaystyle g(x) = -x^2 + 3$


    Find $\displaystyle (g \circ f)(x)$:


    $\displaystyle = g(f(x))$

    $\displaystyle = g(-5x + 2)$

    $\displaystyle = -(-5x + 2)^2 + 3$

    $\displaystyle = - (25x^2 + 4) + 3$

    $\displaystyle = -25x^2 - 4 + 3$

    $\displaystyle = -25x^2 - 1$


    And textbook answer is $\displaystyle (g \circ f)(x) = -25x^2 + 20x - 1$


    I don't know how to get the $\displaystyle "20x" $ ? Please help me !
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor

    Joined
    Aug 2006
    Posts
    21,776
    Thanks
    2823
    Awards
    1
    $\displaystyle - \left( { - 5x + 2} \right)^2 = - \left( {25x^2 - 20x + 4} \right)$
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Composition of Two Functions
    Posted in the Algebra Forum
    Replies: 3
    Last Post: May 14th 2011, 11:26 AM
  2. Composition of Functions
    Posted in the Algebra Forum
    Replies: 2
    Last Post: Feb 22nd 2010, 07:49 PM
  3. Functions / Composition
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: Nov 12th 2008, 03:26 PM
  4. Composition of Functions
    Posted in the Pre-Calculus Forum
    Replies: 2
    Last Post: Sep 14th 2008, 04:41 PM
  5. Composition of Two Functions
    Posted in the Pre-Calculus Forum
    Replies: 1
    Last Post: Jan 9th 2008, 06:44 PM

Search Tags


/mathhelpforum @mathhelpforum