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Question: How do I get dsolve to find the solution without substitution of the first equation

Question:How do I get dsolve to find the solution without substitution of the first equation

Michael_Watson 125 Maple 18
dsolve
February 21 2015
0

 

restart

with(ODETools):

eqn1 := ((diff(f4(r), r))*r-f4(r)*f1(r)+f4(r))/(f4(r)*r^2) = 0

((diff(f4(r), r))*r-f4(r)*f1(r)+f4(r))/(f4(r)*r^2) = 0

 (1)

eqn4 := f4(r)*(r*(diff(f1(r), r))+f1(r)^2-f1(r))/(f1(r)^2*r^2) = 2*m*Dirac(r)*f4(r)/r^2

f4(r)*(r*(diff(f1(r), r))+f1(r)^2-f1(r))/(f1(r)^2*r^2) = 2*m*Dirac(r)*f4(r)/r^2

 (2)

dsolve({eqn1, eqn4})

[{-(2*Dirac(r)*(diff(f4(r), r))^2*m*r^2+4*Dirac(r)*(diff(f4(r), r))*f4(r)*m*r+2*Dirac(r)*f4(r)^2*m-f4(r)*(diff(diff(f4(r), r), r))*r^2-2*(diff(f4(r), r))*r*f4(r))/f4(r) = 0}, {f1(r) = ((diff(f4(r), r))*r+f4(r))/f4(r)}]

 (3)

``

When I try to solve this system of ODE, Maple does not factor out f4(r) in eqn4.  How do I get Maple to solve eqn4? So that I can get the correct result for f1(r) below:

 

dsolve((r*(diff(f1(r), r))+f1(r)^2-f1(r))/(f1(r)^2*r^2) = 2*m*Dirac(r)/r^2)

f1(r) = -r/(2*m*Heaviside(r)-_C1-r)

 (4)

``

Thanks.

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