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Homework Help: 2 chain rules problems

  1. Sep 27, 2011 #1
    For some reason I am struggling with these problems. I am lost as a goose trying to fly south for the winter!

    1. The problem statement, all variables and given/known data

    9^(5-x2)
    and
    another derivative problem using chain rule
    r/square root of the whole term r^2+5

    2. Relevant equations

    1st equation= d/dx= a^x ln a
    2nd equation=

    3. The attempt at a solution

    1st one= -9^(5-x^2) 2x log (9)

    2nd one= i am stuck at square root of (r^2 +5) + square rt (r^2+5) -r^2 all divided by sq root of (r^2+5) all divided by (r^2 +5)^2

    any help would be greatly appreciated!!!
     
  2. jcsd
  3. Sep 27, 2011 #2

    SammyS

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    1st one looks right.

    2nd one: Write using a fractional exponent for square root.

    r/(r2+5)1/2 = r(r2+5)-1/2. Take the derivative of this.
     
  4. Sep 27, 2011 #3
    apparently webassign does not like the answer -9^(5-x^2)2x log (9)

    2. 5/(r^2+5)^3/2
     
  5. Sep 27, 2011 #4
    the second is right :) thanks....now to figure out what is going on with the first one
     
  6. Sep 27, 2011 #5

    SammyS

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    Does WebAssign want log or does it want ln for the log base e ?
     
  7. Sep 27, 2011 #6
    i will try ln base e
     
  8. Sep 27, 2011 #7
    it indeed up being ln
    thanks for your help Sammy S :)
     
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