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logarithms question

Discussion in 'Mathematics' started by bombaysapphire, Mar 17, 2011.

  1. bombaysapphire

    bombaysapphire Star commenter

    n-1 cannot be an even integer because the LHS of your equation is negative meaning the RHS must be negative. Since both sides of the equation are negative then it is valid to multiply both by -1 and make them both postive, then you can take logs.
     
  2. Karvol

    Karvol Occasional commenter

    If the equation has a solution then n cannot be an odd number as anything to an even power is positive. Therefore you know that the negatives can cancel out and thus, after doing that, you can take logs.
    Are you sure the question wasn't 2187?
     
  3. fudgesweets

    fudgesweets New commenter

    oh yes , it is 2187 , thanks...so does that mean in general ln(-a)/ln(-b) is not ln(a)/ln(b)?
     
  4. Karvol

    Karvol Occasional commenter

    You cannot take logs of negatives, so no.
     
  5. To find the (natural) log of a negative number, just remember that e^((N*2+1)*i*pi) = -1 for any integer N.
     

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