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Is this a typo? - Integral of fraction

  1. Jan 2, 2015 #1
    Part (1) of this question posted in post 3. Is it a type-o or correct. Not looking for solution.
     
    Last edited: Jan 2, 2015
  2. jcsd
  3. Jan 2, 2015 #2

    Doug Huffman

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    Gold Member

    Yes, it appears to be so, from what I can see.
     
  4. Jan 2, 2015 #3
    ImageUploadedByPhysics Forums1420232795.902127.jpg
     
  5. Jan 2, 2015 #4
    Forgot the image
     
  6. Jan 2, 2015 #5
    What is a type-o? Or do you think it is a typo? Then type-o probably is a typo.
    The integrals look ok so far.
     
  7. Jan 2, 2015 #6
    Hint for part i): Try to rearrange ##6x^2-5x+3## into some polynome your can divide by ##12x-5## plus a constant.
     
  8. Jan 2, 2015 #7
    Ya I differentiated the top and you get 12x-5 all over 12x-5.
     
  9. Jan 2, 2015 #8
    Ah I see. Could be a typo. But this integral should be solvable as well.
     
  10. Jan 2, 2015 #9
    Part 1&2 only worth 4% on exam paper. Seem like a but of work for 2%
     
  11. Jan 2, 2015 #10
    Private theories are not allowed in this forum. :D But don't worry here. Sorry, I can only look at the math.
     
  12. Jan 2, 2015 #11

    Mark44

    Staff: Mentor

    Anthonyk, why would you think the problem has a typo? This is an easy integral - just divide the numerator by the denominator.
     
  13. Jan 2, 2015 #12
    Lecturer thinks it is because of the low mark. Looking back a previous exam papers made an assumption. If We are wrong I hold my hand up.
     
  14. Jan 2, 2015 #13
    That's are far as I got I had x-1.
     
  15. Jan 2, 2015 #14

    Mark44

    Staff: Mentor

    Last edited: Jan 2, 2015
  16. Jan 2, 2015 #15
    Ya silly mistake by me.
     
  17. Apr 3, 2015 #16
    ImageUploadedByPhysics Forums1428103350.262848.jpg

    Wondering the the solution the this question is right or wrong ?
    Thanks
     
  18. Apr 3, 2015 #17

    mfb

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    What happened in (4)? The denominators vanished?
    Also, what happens if you differentiate your result? Do you get the initial fraction? This is often a very easy check you can always do if you are unsure.

    The whole substitution is not helpful here. Posts 6 and 11 show the best approach.
     
  19. Apr 4, 2015 #18
    This solution is from class. We were given a reason why that were moved but I can remember.
    When studying on my own I divided the polynomial but the devision didn't look right. I'll attempt it again and post later. Thanks.
     
  20. Apr 4, 2015 #19
  21. Apr 4, 2015 #20

    mfb

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    Looks right so far.
     
  22. Apr 4, 2015 #21

    Mark44

    Staff: Mentor

    @anthonyk2013, once you've made it past grade school arithmetic, it's not a good idea to write fractions as mixed numbers (such as you have in your work). Instead of ##1 \frac 1 {24}## or ##1 \frac {23} {24}##, you really should write these as improper fractions, 25/24 and 47/24. Mixed numbers such as the ones you wrote are much harder to work with and can easily be confused if not written very carefully.
     
  23. Apr 4, 2015 #22
    Ill finish later. Too many kids around
     
  24. Apr 4, 2015 #23
    Thanks for the reminder mark44. Long time since i was in grade school as you call it
     
  25. Apr 5, 2015 #24
    ImageUploadedByPhysics Forums1428239530.213025.jpg

    Latest attempt. Wondered if I'm right.
     
  26. Apr 5, 2015 #25

    mfb

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    Integrating x/2 gave x2/2?
    And check what you have in the denominators and logs - but I guess those are just typos.
     
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