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Homework Help: How to start Differential equation

  1. Mar 23, 2014 #1
    Mod note: Thread moved from technical math section. The OP has already been notified that this is not a suitable start to a request for homework help.
    can anyone teach me how to start it? i really have no idea.. PART A

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    Last edited by a moderator: Mar 23, 2014
  2. jcsd
  3. Mar 23, 2014 #2
    You don't need to solve that equation for the two problems
    The first problem amounts to finding a stationary point while the second requires you to implicitly differentiate that expression with respect to time.

    Just a hint for i), the staionary point may only exist in a certain limit.
  4. Mar 23, 2014 #3
    can you show the full working for part i please? i'd been thinking of this question for the whole day yet still cant get the ans
  5. Mar 23, 2014 #4

    Edit: In the last step I just plugged the value of x (which had to be done via a limit since it was positive infinty) back into the original expression for the answer

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  6. Mar 23, 2014 #5
    Note to self: I should really learn LaTeX
  7. Mar 23, 2014 #6
    if i do this way then how should i proceed ? note: i want to find x first , then sub the value of x which i get into the eqaution 1... after arranging the terms, i would get ln 0 ... then i cant find the value of x ...

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  8. Mar 23, 2014 #7
    At the last step, you need to realize that the only way for the left hand side to equal zero is when x tends to positive infinity.
  9. Mar 23, 2014 #8
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