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Combining functions - just another check

  1. Apr 20, 2004 #1
    combining functions - just another check :)

    f(x) = 2/x
    g(x) = x/x+2

    fog = f(g(x))
    = f(x/x+2)
    =2 * x+2/x

    [Edit (by ahrkron): no changes; took back my edit (I meant to reply)... the post is now in its original form]
    Last edited by a moderator: Apr 21, 2004
  2. jcsd
  3. Apr 20, 2004 #2
    Better recheck the last two equations.
    2*(x+2)/x is what you meant, is it not?
  4. Apr 21, 2004 #3


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    Staff Emeritus
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    Be careful. Use parentheses, and you most probably need to think about the domain of both functions (what values of x are excluded on each case? what about the composition?).
  5. Apr 21, 2004 #4
    oh ya, I forgot to distribute the 2

    how would I find the domain ahrkron :redface:
  6. Apr 21, 2004 #5
    For what values of x are f(x) and g(x) undefined? Those will be out of the domain.

  7. Apr 21, 2004 #6

    matt grime

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    The domain should be given otherwise it isnt' a function. At some point teachers and basic text book writers are going to learn this.
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