Rewriting Equations with ln and Exponential Terms

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Homework Help Overview

The discussion revolves around solving the equation ln(1+e^x)=2 for the variable x, focusing on the manipulation of logarithmic and exponential terms.

Discussion Character

  • Conceptual clarification, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants explore the steps taken to isolate x, questioning the necessity of reintroducing the natural logarithm in the final expression. There is also a mention of potential typos in the original equations.

Discussion Status

The conversation reflects a mix of understanding and confusion regarding the manipulation of logarithmic expressions. Some participants express clarity after receiving feedback, while others continue to seek confirmation on their reasoning.

Contextual Notes

Participants note the importance of maintaining the natural logarithm in the final answer, indicating a potential misunderstanding of logarithmic properties and their implications in the solution process.

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Homework Statement


I have to solve ln(1+e^x)=2 for x

Homework Equations

The Attempt at a Solution


ln(1+e^x)=2
ln(1+e^x)=lne^2
(1+e^x)=e^2
e^x=e^2-1
x=(e^2-1)

The real answer is x=ln(e^2-1) but I don't understand why we have to put the ln back? why can't we keep it like that x=(e^2-1).

thank you very much
 
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masterchiefo said:

Homework Statement


I have to solve ln(1+e^x)=2 for x

Homework Equations

The Attempt at a Solution


ln(1+e^x)=2
ln(1+e^x)=e^2
That should be e^ln(1+e^x) = e^2

Maybe it's a typo.
(1+e^x)=e^2
e^x=e^2-1
Take the natural log of both sides !

x=(e^2-1)

The real answer is x=ln(e^2-1) but I don't understand why we have to put the ln back? why can't we keep it like that x=(e^2-1).

thank you very much
 
SammyS said:
That should be e^ln(1+e^x) = e^2

Maybe it's a typo.

Take the natural log of both sides !
ln(1+e^x)=2
ln(1+e^x)=lne^2 -- forgot to add the ln there.
then I take out ln on both side then at the end I basically have to add ln back to reduce it to x?
 
masterchiefo said:
ln(1+e^x)=2
ln(1+e^x)=lne^2 -- forgot to add the ln there.
then I take out ln on both side then at the end I basically have to add ln back to reduce it to x?
The "both sides" refers to the following from your Original Post.
masterchiefo said:
e^x=e^2-1

From the above line to that below,
Take the natural log of both sides !​

x ( e^2-1)
 
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SammyS said:
The "both sides" refers to the following from your Original Post.
OHH sorry my bad, thank you very much, I understand now :)
 

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