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Question about reducing an answer from a derivative?

  1. Feb 12, 2014 #1
    Ok, I can get to the answer in yellow, but I am not sure how they went from the answer in yellow to the simplified one in white. I really need to know how to do this because we are using these derivatives for magnitudes (solving for principal normal unit vectors), where I have to square them and take square roots. So, I'm sure you could imagine having to square equations like this, factor out, try to take roots, etc., is a complete and utter nightmare. Each problem is taking me about 30-40mins, and there are 9 homework problems.

    Anyway, here is the derivative:

    a_Screen_Shot.jpg

    b_Screen_Shot.jpg
     
  2. jcsd
  3. Feb 12, 2014 #2

    Simon Bridge

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    Put your two terms over a common denominator, expand the brackets and extract 4t^3 as a common factor in the numerator.
     
  4. Feb 12, 2014 #3
    Ah, ok I see it now. Thanks again!
     
  5. Feb 12, 2014 #4

    Simon Bridge

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    No worries. Well done.
     
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