Calc 2: Problems with an ODE

icedpolonium

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Sep 10, 2015
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Hello :)

I'm having difficulties with the following differential equation:
y=ex2log(y2)\displaystyle y'={e^{x^2}}\log(y-2)

I tried to solve it by separating the variables (y>2,y3\displaystyle y>2, y \neq 3):

yx=ex2log(y2)\displaystyle \frac{\partial y}{\partial x}={e^{x^2}}\log(y-2)
yx1log(y2)=ex2\displaystyle \frac{\partial y}{\partial x}\frac{1}{\log(y-2)}={e^{x^2}}

and then I'm stuck after trying to integrate both sides with respect to x:

ylog(y2)=ex2x\displaystyle \int \frac{\partial y}{\log(y-2)}=\int {e^{x^2}} \partial x

In fact, I can't integrate even one of them :(


If it is of any help, the ODE was part a Cauchy problem, with y(0)=3\displaystyle y(0)=3 being the condition to satisfy.


Am I missing something?
 
Hello :)

I'm having difficulties with the following differential equation:
y=ex2log(y2)\displaystyle y'={e^{x^2}}\log(y-2)

I tried to solve it by separating the variables (y>2,y3\displaystyle y>2, y \neq 3):

yx=ex2log(y2)\displaystyle \frac{\partial y}{\partial x}={e^{x^2}}\log(y-2)
yx1log(y2)=ex2\displaystyle \frac{\partial y}{\partial x}\frac{1}{\log(y-2)}={e^{x^2}}

and then I'm stuck after trying to integrate both sides with respect to x:

ylog(y2)=ex2x\displaystyle \int \frac{\partial y}{\log(y-2)}=\int {e^{x^2}} \partial x

In fact, I can't integrate even one of them :(


If it is of any help, the ODE was part a Cauchy problem, with y(0)=3\displaystyle y(0)=3 being the condition to satisfy.


Am I missing something?

let z = log(y-2) → y-2 = ez

dy/dx = ez * dz/dx

ez * dz/dx * z = e^{x^2}

Now you should know

integral e^(x^2) dx = 1/2 sqrt(pi) erfi(x)+constant

and continue..
 
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