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Need help with using Leibniz's Rule

  1. Dec 17, 2015 #1
    I tried solving this question but I'm not getting the correct answer and I don't know what I'm doing wrong. Can anyone tell me what I did wrong? Thank you.

    The math question is:
    Let g(x) = d/dx (∫x21 et/t dt), then g'(2) is ____?

    The correct answer is e4 but I'm getting 7e4/2. (See my solution attempt in the attached PDF file.)

    Attached Files:

  2. jcsd
  3. Dec 17, 2015 #2


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    I get the same result as you. Maybe we made the same mistake, or maybe the question was to find ##g(2)##.
  4. Dec 17, 2015 #3
    Thank you for your reply.
    The sample question specifically asks for g'(2) but what you say seems to make sense.
    (Although, that would be a he** of a mistake on the part of the school since it's the one of last year's exam questions. :/ )
  5. Dec 17, 2015 #4


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    Well, everybody can make mistakes. Maybe we did, maybe the school did. Let's wait for others to check the computation.
  6. Dec 21, 2015 #5
    If you let g(x) be the integral only. Then the derivative of g(x) at x=2 is e^4. Probably transcription error somewhere.
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