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Thread: A function

  1. #1
    Junior Member
    Joined
    May 2009
    Posts
    25

    A function

    Given:
    $\displaystyle f(x)=\sqrt{x}$ and $\displaystyle g(x)=x^2-1$

    How can I evaluate something like:
    $\displaystyle f(g(2))$ or $\displaystyle g(f(0))$

    I seem to get confused whenever they throw a number in the composite. Like I know how to evaluate $\displaystyle f(g(x))$ but I'm not sure what to do when they place a number in it. :/
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  2. #2
    Newbie darthfader's Avatar
    Joined
    Apr 2009
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    Philippines
    Posts
    10
    Hi jimmyp

    Evaluating composite functions such as $\displaystyle f(g(x))$ is just simply evaluating the $\displaystyle g(x)$ first and then taking the value of $\displaystyle g(x)$ as the new 'x' and then evaluate $\displaystyle f(x)$.

    To illustrate what I'm talking about, I'll do the first one for you.

    Given:
    and



    $\displaystyle g(2) = 2^2 -1 = 3$
    since $\displaystyle g(2) = 3$ then $\displaystyle f(g(2)) = f(3)$

    Hence...
    $\displaystyle f(3) = \sqrt{3}$

    I hope this helps.

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