How to Simplify the Solution of y' = 6y ln(y)/x?

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Homework Help Overview

The discussion revolves around solving the differential equation y' = 6y ln(y)/x, focusing on the integration and simplification of the resulting expressions.

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts separation and integration, expressing uncertainty about simplifying the result into an explicit form for y. Other participants explore the implications of redefining constants during the integration process.

Discussion Status

Participants are actively engaging with the problem, with some suggesting alternative approaches to simplify the expression. There is a recognition of the importance of correctly handling logarithmic properties, and a collaborative effort to clarify the manipulation of constants.

Contextual Notes

There is an acknowledgment of potential confusion regarding the treatment of constants during integration, as well as the complexity of achieving a clean explicit form for y.

Saladsamurai
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Solve:

[tex]y' = 6\frac{y\ln y}{x}[/tex]

After separation and integration, I got

[tex]\ln[\ln y] = 6\ln x + c_1[/tex]

[tex]\Rightarrow \ln y = e^{\ln x^6 + c_1}[/tex]

I am not sure how to get this into an explicit form for y, without it getting nasty. I know that there is usually a trick to make it look cleaner.

Any thoughts?
 
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On a whim, I let [itex]c_1 = \ln c_2[/itex] and good things happen! I get,

[tex]y = e^{\frac{x^6}{c_2}}[/tex]
 
Acutally, if you let [itex]c_1= ln(c_2)[/itex] then you would have [itex]ln(x^6)+ c_1= ln(x^6)+ ln(c_2)= ln(c_2x^6)[/itex] so that
[tex]ln(y)= e^{ln(c_2x^6)}= c_2x^6[/tex]
and
[tex]y= e^{c_2x^6}[/tex].

That is, [itex]c_2[/itex] is multiplying [itex]x^6[/itex], not dividing it. But since it is simply an arbitrary constant, it really does not matter.
 
Oops! It was a summation of logs! Not a difference ... Nice catch Halls! :smile:
 

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