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Math Help - Domain Problem and Inverse Problem

  1. #1
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    Domain Problem and Inverse Problem

    I need a little help here !!!

    3) Find the domain of

    f(x) = sqrt x / (ln (x^2 + 1) - 17) i don't know how to do this ..please use union

    4) Find inverse f(x) = e^x^3 - 2 the -2 is not beside 3 it is beside x....i got cube root 3 of lnx + 2

    Thanks
    Last edited by Ackbeet; September 8th 2011 at 04:38 PM. Reason: Splitting.
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  2. #2
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    Re: Domain Problem and Inverse Problem

    "Domain" is usally defined in terms of the GREATEST set of values. This makes it most convenient, very often, to consider a very GREAT set of values. Try starting with "All Real Numbers" and see what must be discarded.

    ln(x) requires x > 0

    sqrt(x) requires x >= 0

    1/x requires x <> 0

    What say you?
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  3. #3
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    Re: Domain Problem and Inverse Problem

    Quote Originally Posted by qwerty999 View Post
    I need a little help here !!!

    3) Find the domain of

    f(x) = sqrt x / (ln (x^2 + 1) - 17) i don't know how to do this ..please use union

    4) Find inverse f(x) = e^x^3 - 2 the -2 is not beside 3 it is beside x....i got cube root 3 of lnx + 2

    Thanks
    Assuming you mean " f(x)= e^{x^3}}- 2" and not " f(x)= (e^x)^3- 2" which would be more simply written " f(x)= e^{3x}- 2", and assuming you mean "cube root of (ln(x+ 2))" and not "cube root of (ln(x)+ 2)" or "cube root of (ln(x))+ 2", yes, that is correct.
    Please use parentheses to clarify what you mean!

    But what in the world is "cube root 3 of "??? I assume you mean just "cube root". "third root" would mean the same. Never use the unfortunate notation "root 3" or worse "squareroot 3" which I have seen before. Both of those would mean "square root of 3 times...".
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