Seperable Differential equation

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SUMMARY

The discussion focuses on solving the separable differential equation dm/ds = m with the initial condition m(1) = 7. The solution process involves integrating both sides, resulting in ln|m| = s + k, where k is a constant derived from the integration. The user successfully derives m(s) = e^(s+k) and determines that e^k = 7e^{-1}, leading to the final expression m(s) = 7e^(k-1). The conversation highlights the importance of combining constants of integration for clarity.

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nick.martinez
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dm/ds=m ; m(1)=7

when i find the diff eq

∫dm/m=∫ds

ln|m|+c1=s+c2 ; k=c2-c1

ln|m|=s+k
e ^ both sides

m(s)=e^(s+k) ; m(1)=7

m(1)=e^(1)*e^(k)=7
i am stuck here. not sure how to proceed please help.
 
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What are you trying to figure out with your initial condition?

Can you solve this equation using another technique?
 
nick.martinez said:
dm/ds=m ; m(1)=7

when i find the diff eq

∫dm/m=∫ds

ln|m|+c1=s+c2 ; k=c2-c1
There is really no need to write both c1 and c2. It's perfectly proper to immediately combine the two "constants of integration" to write ln|m|= s+ k.

ln|m|=s+k
e ^ both sides

m(s)=e^(s+k) ; m(1)=7

m(1)=e^(1)*e^(k)=7
i am stuck here. not sure how to proceed please help.[/QUOTE]
So e^k= 7e^{-1}.

e^(s+k)= e^k e^s so m(s)= 7e^{-1}e^k or m(s)= 7e^(k-1).
 

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