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Math Help - Limits question (multiple choice)

  1. #1
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    Limits question (multiple choice)

    I'm not really sure what it is asking me

    lim -->5+ \sqrt{5-x}=?

    The provided answers are

    a.) not real
    b.) 0
    c.) 1
    d.) none of these

    I feel like it is 0. Since 5-5 is 0. Could someone help me here?
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  2. #2
    Junior Member ihmth's Avatar
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    Is that all the informtion? I think it should give the value of x.
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  3. #3
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    That might be what is confusing me it does have lim x---->5+. The teacher said that is X from the positive side
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  4. #4
    Junior Member ihmth's Avatar
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    so maybe the function is \sqrt{5-x} and its asking for the value of the function as it approaches to 5. if that's the case, the answer will be 0.
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  5. #5
    Junior Member ihmth's Avatar
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    wait, im not really sure about this. there is also a possibility that the answer will not be 0, because if you will graph it:

    Limits question (multiple choice)-grph.bmp
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  6. #6
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    That is a good point. I might just ask the teacher to clarify. I appreciate your help
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  7. #7
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    Quote Originally Posted by XIII13Thirteen View Post
    lim -->5+ \sqrt{5-x}=?
    The provided answers are
    a.) not real b.) 0 c.) 1 d.) none of these
    Strickly speaking the answer would have to be (d.).
    The function is not even defined for (5+).
    However given how sloppy things have gotten, the expected answer may be (a).
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  8. #8
    Super Member wingless's Avatar
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    \lim_{x\to 5^{+}} \sqrt{5-x}


    Graph:



    It's a one sided limit. What does it approach while x goes to 5 from left? It doesn't approach anywhere because f(x) isn't defined for x>0 !
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  9. #9
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    The limit does not exist. By definition, the limit must be a real number. I agree with Plato in that the correct choice must be (d). To say "such and such limit is not real" would be a very ambiguous statement. Is it implying that the limit exists, but is not a real number?. Or, is it implying that "not real" is the same thing as "does not exist"? Either way, it is still worth clarifying with your teacher what he/she thinks is the correct answer so you don't get points taken off of an exam for being "too correct". It comes down to semantics.
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