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Homework Help: Help solving a ln equation

  1. Jul 28, 2006 #1

    dnt

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    ln (x+1) = x-3

    i know ln is log base e so the equation becomes:

    e^(x-3) = x + 1

    and i can rearrange using algebra to get:

    e^x = e^3(x+1)

    but now im stuck...how can i separate the x's to solve for it?

    thanks.
     
  2. jcsd
  3. Jul 28, 2006 #2

    StatusX

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    Homework Helper

    You can't write the solution x in terms of elementary functions like e^x and ln(x). You'll probably have to use a calculator to get an approximate numerical solution.
     
  4. Jul 28, 2006 #3

    dnt

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    ah thanks.
     
  5. Jul 29, 2006 #4

    HallsofIvy

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    Science Advisor

    In general, there is no "algebraic" solution for problems that involve both a transcendental function of x (such as ex) and non-transcendental function of x (such as x+1). You will have to use some approximation method (such as graphing y= ex-3 and y= x+1 and seeing where they cross).
     
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