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Math Help - Log question: no one could do this in class

  1. #1
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    Log question: no one could do this in class

    no one could do this in class, not even the teacher.

    5^x + 3^2x = 92

    solve for x

    Ans: x=1.93 which works, but how do you get it?
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  2. #2
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    Quote Originally Posted by white_cap View Post
    no one could do this in class, not even the teacher.

    5^x + 3^2x = 92

    solve for x

    Ans: x=1.93 which works, but how do you get it?
    Hello,

    if you only want to get a value for x use Newton-Raphson method:

    x_n=x_{n-1}-\frac{5^{x_{n-1}}+9^{x_{n-1}}-92}{\ln(5) \cdot 5^{x_{n-1}}+\ln(9) \cdot 9^{x_{n-1}}}

    Start with
    x_0 = 2 The following values are:

    1.935841955
    1.931141625
    1.931118438
    1.931118437
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  3. #3
    is up to his old tricks again! Jhevon's Avatar
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    Quote Originally Posted by earboth View Post
    Hello,

    if you only want to get a value for x use Newton-Raphson method:

    x_n=x_{n-1}-\frac{5^{x_{n-1}}+9^{x_{n-1}}-92}{\ln(5) \cdot 5^{x_{n-1}}+\ln(9) \cdot 9^{x_{n-1}}}

    Start with
    x_0 = 2 The following values are:

    1.935841955
    1.931141625
    1.931118438
    1.931118437
    i thought as much. i don't see how you could use logs to solve this by hand
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