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Help me check my work (limit problem)

  1. Apr 20, 2012 #1
    1. The problem statement, all variables and given/known data
    Hey I just need someone to check my work to make sure I did it right, thanks.

    y9isi.png

    26K55.png

    A9GNY.png

    cpUZc.png


    3qRXa.png
     
  2. jcsd
  3. Apr 20, 2012 #2

    Mark44

    Staff: Mentor

    The step above has an error. ln <whatever> ≠ eln<whatever>.

    Also, how did you go from (1 - 3/x)2x + 10 to (-3/x *2x + 10)?

    Finally, eln(-6) ≠ -6, because ln(-6) is undefined.
     
  4. Apr 20, 2012 #3

    Mark44

    Staff: Mentor

    I should mention that posting a bunch of images of the work you've done makes it much more difficult to point out where errors happen to be. Using LaTeX you can format your work exactly as you have it in the images you uploaded.
     
  5. Apr 20, 2012 #4
    Sorry but typing in latex takes too long so i just cropped the pics straight from my doc file

    from this formula in my textbook:
    9xMqB.jpg
    Anyway seeing as my answer is wrong how should i go about this problem?
     
  6. Apr 20, 2012 #5

    Mark44

    Staff: Mentor

    What turns out to be a convenience for you is inconvenient for me, and possibly others at this site whose help you are seeking.
    Are you sure you typed the formula correctly? I've never seen the formula that you wrote, and I'm pretty sure it is incorrect.
    Your answer is correct, but you work along the way is not for the reasons I already gave.

    The easiest thing to do is to rewrite ln(1 - 3/x)2x + 10 as (2x + 10)*ln(1 - 3/x), and then rearrange so that you can use L'Hopital's Rule.
     
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