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Thread: (fog)(x) and (gof)(x)

  1. #1
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    (fog)(x) and (gof)(x)

    Consider the functins f(x) = the square root of x + 3

    and

    g(x) = x^2 - 3.

    a) (fog) (x)


    b) (gof) (x)


    c) (f+g) (x)


    d) (fg) (x)


    I know the rules for combing the functions:


    Can somebody help check behind me on c) and d) and show me a) and b)?

    Thanks again. K
    Kaye

  2. #2
    Senior Member
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    Re: (fog)(x) and (gof)(x)

    [tex]f(x) = \sqrt{x+3}\\ g(x) = x^2-3[/tex]



    a) (fog) (x)
    [tex]f(g(x)) = \sqrt{g(x)+ 3} = \sqrt{x^2-3+3} = |x|[/tex]


    b) (gof) (x)
    [tex]g(f(x)) = (\sqrt{x+3})^2 - 3 = ...[/tex]


    c) (f+g) (x)
    [tex]f(x) + g(x) = ...[/tex]


    d) (fg) (x)
    [tex]f(x) \times g(x) = ...[/tex]

  3. #3
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    For:

    a) (fog) (x) = 400.07 ?

    b) (gof) (x) = 400 ?

    c) (f = g) (x) = 400.500 ? ?

    d) (fg) (x) = 693.107 ? ? ?

    Correct?

    K
    Kaye

  4. #4
    Senior Member
    Join Date
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    1,307
    Quote Originally Posted by kjones
    For:

    a) (fog) (x) = 400.07 ?

    b) (gof) (x) = 400 ?

    c) (f = g) (x) = 400.500 ? ?

    d) (fg) (x) = 693.107 ? ? ?

    Correct?

    K
    How can we check if you haven't given us an x value?

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