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More Complex Logarithm and advanced Math Questions

  1. Aug 21, 2011 #1
    Hello, was wondering if anyone could please help me with the following questions as for math I have been given a substitute teacher who is of little help.

    Any help would be much appreciated, even if its just pointing me in the right direction

    Equation 1:

    Log (x-3) = 1 + Log 4 - Log x


    Equation 2:

    2-4a + 2 x 2-2a - 8 = 0


    Equation 3:

    Without using calculator, find the value of A that makes x = e^12 / 1-2e^12 a solution of the equation:

    ln x - ln (ax+1) = 12




    Thanks again Jake
     
  2. jcsd
  3. Aug 21, 2011 #2

    eumyang

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    Re: Logarithm Questions - Advanced Math B Help

    Equation 1:
    [itex]\log (x-3) = 1 + \log 4 - \log x[/itex]
    Rewrite 1 as a logarithm. Use the properties of logarithms to combine the logs on the right side into a single logarithm. Then "drop" the log from both sides, and solve.

    Equation 2:
    This is unreadable. What does the "-" right before the 4a and 2a mean? Are they subtractions? And is the "x" a variable or multiplication?

    Equation 3:
    [itex]\ln x - \ln (ax+1) = 12[/itex]
    Similar to #1. Rewrite 12 as a natural logarithm. Use the properties of logarithms to combine the logs on the left side into a single logarithm. Then "drop" the ln from both sides, and solve.
     
  4. Aug 21, 2011 #3
    Re: Logarithm Questions - Advanced Math B Help

    Thanks for your fast reply

    Sorry Equation 2 is as follows, as the power symbol didnt work:

    2-4a + 2 x 2-2a - 8 = 0

    Thanks again
     
  5. Aug 22, 2011 #4

    Ray Vickson

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    Re: Logarithm Questions - Advanced Math B Help

    Again: is the "x" a variable, or is it a multiplication sign? If you mean multiplication, it would be much better to use an asterisk (*), like this: 2^(-4a) + 2*2^(-2a) - 8 = 0.

    RGV
     
  6. Aug 22, 2011 #5

    PeterO

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    Re: Logarithm Questions - Advanced Math B Help

    Let U = 2-2a; substitute, solve for u then find solutions for x
     
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