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Math Help - [SOLVED] logarithmic equation

  1. #1
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    [SOLVED] logarithmic equation




    Help me, please?
    Last edited by Waat; February 25th 2009 at 12:49 PM.
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  2. #2
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    Quote Originally Posted by Waat View Post


    I managed to get to that point, have no idea what to do now.



    Help me, please?
    Hi

    I am afraid this equation cannot be solved without a calculator.
    Are you sure you need to solve it ?
    Are you allowed to use a calculator ?
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  3. #3
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    Quote Originally Posted by running-gag View Post
    Hi

    I am afraid this equation cannot be solved without a calculator.
    Are you sure you need to solve it ?
    Are you allowed to use a calculator ?
    Yeah, without a calculator.
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  4. #4
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    Quote Originally Posted by Waat View Post


    I managed to get to that point, have no idea what to do now.



    Help me, please?
    Please post the original question.
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  5. #5
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    Made a mistake , it(the original equation) should be
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  6. #6
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    Quote Originally Posted by Waat View Post
    Made a mistake , it(the original equation) should be
    The first thing I'd do is try a value of x that gives a nice value for 27^x. So try x = 1/3 ....

    (There is no formal algebraic way of doing this question, it has to be done in a way like I have suggested above).
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  7. #7
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    Quote Originally Posted by mr fantastic View Post
    The first thing I'd do is try a value of x that gives a nice value for 27^x. So try x = 1/3 ....

    (There is no formal algebraic way of doing this question, it has to be done in a way like I have suggested above).
    I've just asked a really smart guy. He suggested using the lambert w function. Thanks for help anyway.
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  8. #8
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    Quote Originally Posted by Waat View Post
    I've just asked a really smart guy. He suggested using the lambert w function. Thanks for help anyway.
    I feel like such a dope suggesting that the solution could be easily found be inspection.

    Actually I was going to suggest the Lambert W-function could be used to get a formal algebraic solution but:

    1. I didn't think you had the mathematical background to understand this and didn't want to cause confusion.

    2. I didn't want to use an elephant gun to kill a fly.

    You will find MHF has many threads showing how the Lambert W-function can be used to solve equations eg.

    http://www.mathhelpforum.com/math-he...need-help.html

    http://www.mathhelpforum.com/math-he...-equation.html

    http://www.mathhelpforum.com/math-he...g-ln-x-kx.html

    http://www.mathhelpforum.com/math-he...ed-itself.html

    You should have no trouble applying the same idea to your question. You will still get x = 1/3 as the answer but at least you'll be able to justify the solution algebraically.
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