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Homework Help: Problem with solving 'basic formula' derivatives

  1. Sep 25, 2010 #1
    1. The problem statement, all variables and given/known data

    [PLAIN]http://webwork2.asu.edu/webwork2_files/tmp/equations/9f/ab106661843d52ded597f9bcb68ace1.png [Broken] find f'(x)

    2. Relevant equations



    3. The attempt at a solution

    I tried 8x^.5(-4), 0, and a few others once my original try came up with nothing. I realize sqrtx should come out as .5x^-.5, x should be 1 but i'm not sure how to use the 16 and -5 for sure.

    I tried a couple others deeper into the assignment and ran into the same problems

    1. The problem statement, all variables and given/known data
    [PLAIN]http://webwork2.asu.edu/webwork2_files/tmp/equations/af/00b3090b142ffad24c374c5457d8701.png [Broken]


    2. Relevant equations



    3. The attempt at a solution

    This one i got (12x+12)/(.5x^-.5) which is wrong also.


    In addition to helping me with those problems and simple rules that i'm forgetting would be great help. I know i must be missing something amazingly simple. On a side note this is online work that doesn't require you to simplify so I know its not going to be that.

    Thanks!
     
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 25, 2010 #2

    Doc Al

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    Staff: Mentor

    Are you familiar with the product and quotient rules?

    See: http://people.hofstra.edu/stefan_waner/Realworld/tutorials/unit3_1.html [Broken]
     
    Last edited by a moderator: May 4, 2017
  4. Sep 25, 2010 #3

    cristo

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    Staff Emeritus
    Science Advisor

    How do you think you should try and solve the problems? Have you tried using the product rule?

    [Wow, beaten by a split second!]
     
  5. Sep 25, 2010 #4
    Thanks so much, got through those problems with a breeze. The problems were under 2.3 while the rules were under 2.4 in our book, so i didn't think to look there.

    I have a new problem though;

    [PLAIN]http://webwork2.asu.edu/webwork2_files/tmp/equations/d2/30fb1bbeb9b92f7b1e0062bfe44f211.png [Broken]
    I need to find f'(x) in this one also and i went about it by doing the product rule on the left and the quotient rule on the right. This is what i got multiple times:
    [PLAIN]http://webwork2.asu.edu/webwork2_files/tmp/equations/59/803e4ab45c0a518b7e25421e0ea89d1.png [Broken]
     
    Last edited by a moderator: May 4, 2017
  6. Sep 26, 2010 #5

    Doc Al

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    Staff: Mentor

     
    Last edited by a moderator: May 4, 2017
  7. Sep 26, 2010 #6
    what i would do in these situations is combine the exponents in all of these problems.
    for example, x^4 times x^0.5 would be x^4.5, or x^(9/2).

    doing this is an excellent strategy that allows you to avoid any product or quotient rules, and seeing that these problems are appearing in your book before the chapters on these two rules, i would do it this way instead.
     
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