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What are the steps that I take to solve the following exponential equation:

 

e^x - 12^(e-x) - 1 = 0

 

I currently have gotten this far, but need assistance, as my method has gotten me the wrong answer:

 

e^x - 12^(e-x) - 1       =            0                               Original exponential equation.

e^x - 12^(e-x)            =            1                               Add 1 to both sides of equation to isolate the exponential stuff.

      -12^(e-x)             =            1 - e^x                       Subtract e^x on both sides of equation to isolate 12^(e-x)

       12^(e-x)             =             e^x - 1                      Multiply both sides of the equation by -1.

 log[12^(e-x)]            =       log(e^x - 1)                    Take common log of both sides, to start isolating x.

 log(12) * (e-x)         =       log(e^x - 1)                     Property of Logarithms: Coefficients and Exponents. Simplify.

               e - x          =       log(e^x - 1) - log(12)      Subtract log(12) on both sides to isolate e - x.

               e - x          =       log[(e^x - 1) / 12]            Property of Logarithms: Subtraction & Quotients. Simplify.

                   -x          =  ln {log[(e^x - 1) / 12]}           Take the ln of both sides of equation to isolate x.

                    x          = -ln {log[(e^x - 1) / 12]}           Multiply both sides of equation by -1 to find what x is.

 

The reason I know this is wrong, aside from the unnecessary problem of having to take ln of a log of a quotient, is because the website I must submit my answer to says the answer is a whole number. Any help would be appreciated, and if it is difficult to read anything, I sincerely apologize.

 

NOTE: If I divided both sides of the equation by log(12) on step 6, I would have ended up in the same place as I was in step 8. I was aware of this error, but if I came up with the same solution as the one if I did divide both sides of the equation by log(12), even with mathematics strict rules, it still works out in this situation.

 Sep 25, 2016
 #1
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My computer, using iteration and interpolation, comes out with this value for x:

x ≈ 1.98086

 Sep 25, 2016
 #2
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Do this by turning the equation into a quadratic as follows:

 

.

 Sep 25, 2016
 #3
avatar+33616 
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Note:  I've assumed the equation is meant to be: e^(x) - 12*e^(-x)  - 1 = 0,  which is different from the way the original is written.

.

Alan  Sep 25, 2016

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