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Homework Help: Solve log(x) + log(x+3) = 1

  1. Nov 22, 2008 #1
    1. The problem statement, all variables and given/known data

    logx+log(x+3)=1

    2. Relevant equations



    3. The attempt at a solution

    Ive tried to put it in solve so i know x=2

    i think i have to, hmm i dont know if its called differantiate in english but i dont know how to differantiate log.


    Edit: this is what ive tried after differantiating

    1/x+1/x=1
    that means it must be 2 since 2 halfs give 1
     
    Last edited: Nov 22, 2008
  2. jcsd
  3. Nov 22, 2008 #2

    Hootenanny

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    Re: logx+log(x+3)

    Welcome to Physics Forums.

    I'm guessing that you're trying to solve for equation to find x?
     
  4. Nov 22, 2008 #3
    Re: logx+log(x+3)

    yes, sry for my bad explaining of my problem
     
  5. Nov 22, 2008 #4

    Hootenanny

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    Re: logx+log(x+3)

    No problem.

    When attempting to solve equations, usually the best thing to do is to collect all the terms you want together. So can you combine the two log terms into a single logarithm?
     
  6. Nov 22, 2008 #5

    Mark44

    Staff: Mentor

    Re: logx+log(x+3)

    This problem has nothing to do with differentiation. All you need to know are the properties of logarithms and how to factor quadratics.
     
  7. Feb 5, 2011 #6
    Re: logx+log(x+3)

    I know this is an old post but incase people find it in the future:

    rule 1)
    logbx + logby = logbxy

    rule 2)
    x (x + a) = x2 + ax

    rule 3)
    solving quadratic equations
     
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