Status: Accepted
Owner: asmeurer
CC: smichr
Labels: Type-Defect Priority-Medium Solvers
New issue 2077 by asmeurer: classify_ode() doesn't catch a 1st_linear ode
http://code.google.com/p/sympy/issues/detail?id=2077
It seems that we didn't do a good enough job of fixing issue 1650. If you
rearrange this ODE, you will find that it is indeed 1st_linear
(f(x).diff(x) + g(x)*f(x) + h(x)).
In [47]: diff(f(x), x)/(k*f(x) + k*x*f(x)) + 2*f(x)/(k*f(x) + k*x*f(x)) +
x*diff(f(x), x)/(k*f(x) + k*x*f(x)) + z
Out[47]:
d d
──(f(x)) x⋅──(f(x))
dx 2⋅f(x) dx
z + ───────────────── + ───────────────── + ─────────────────
k⋅f(x) + k⋅x⋅f(x) k⋅f(x) + k⋅x⋅f(x) k⋅f(x) + k⋅x⋅f(x)
In [48]: classify_ode(diff(f(x), x)/(k*f(x) + k*x*f(x)) + 2*f(x)/(k*f(x) +
k*x*f(x)) + x*diff(f(x), x)/(k*f(x) + k*x*f(x)) + z, f(x))
Out[48]: (1st_exact, 1st_exact_Integral)
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