Why Does My Differential Equation Solution Differ from the Textbook's?

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SUMMARY

The discussion centers on the differential equation \(\frac{\mathrm{dy}}{\mathrm{d}x} = \frac{x - e^{-x}}{y + e^{y}}\). The user initially integrated the equation and arrived at \(\frac{1}{2}y^{2} + e^{y} = \frac{1}{2}x^{2} + e^{-x} + c\). However, the textbook solution presents the equation as \(y^{2} - x^{2} + 2(e^{y} - e^{-x}) = c\). The discrepancy arises from the user's integration process, where they neglected to multiply through by 2 to eliminate the fractions, leading to a different representation of the same solution.

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Homework Statement



\[\frac{\mathrm{dy} }{\mathrm{d} x} = \frac{x - e^{-x}}{y + e^{y}}<br /> \]


Homework Equations



The Attempt at a Solution



This is how I did it...
[1] multiple
\[y + e^{y} (dy) = x - e^{-x} (dx)\]

[2] integrate both sides and I get
\[\frac{1}{2}y^{2} + e^{y} = \frac{1}{2}x^{2} + e^{-x} +c\]

However, the solution gives
\[y^{2} - x^{2} +2(e^{y} - e^{-x}) = c\]
Notice the 2? I can't figure out what I did wrong.

I thank for any helps in advance!
Thanks.
 
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They just solved for c, then multiplied through by 2 to eliminate the 1/2's.
 
c is an arbitrary constant, your equation is the same as their's but, with 2c \rightarrow c. You are free to rename your arbitrary constants, as long as you do it consistently all throughout the equation.
 

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