Comment #7 on issue 1305 by [email protected]: sympy.roots not working for
slightly more complicated polynomials
http://code.google.com/p/sympy/issues/detail?id=1305
not sure how we should check for exact result, as the output formula is
really
unreadable ...
and check the result by subtituing and equaling to zero:
In [6]: r = roots( x**2*(a + b*(c-d)*a) + x*a*b*c/(b*d-d) + (a*d-c/d), x)
In [7]: ( x**2*(a + b*(c-d)*a) + x*a*b*c/(b*d-d) + (a*d-c/d)).subs(x,
r.values()[0])
Out[7]:
c a⋅b⋅c
a + a⋅d + a⋅b⋅(c - d) - ─ + ────────
d -d + b⋅d
but this is not an identity:
In [8]: _.expand().subs(a,1).subs(b,0).subs(c,0).subs(d,1)
Out[23]: 2
Maybe i'm doing something wrong. Maybe I've encountered a bug.
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