Status: New
Owner: ----
Labels: Type-Defect Priority-Medium
New issue 4003 by spoo...@abv.bg: Cannot return general quartic solution
http://code.google.com/p/sympy/issues/detail?id=4003
What I am trying to do is this:
In [1]: var('a b c d e x')
Out[1]: (a, b, c, d, e, x)
In [2]: solve( a*x**4 + b*x**3 + c*x**2 + d*x + e , x )
But there is this error:
---------------------------------------------------------------------------
PolynomialError Traceback (most recent call last)
<ipython-input-2-5df3c8dd7670> in <module>()
----> 1 solve( a*x**4 + b*x**3 + c*x**2 + d*x + e , x )
/usr/local/lib/python2.7/dist-packages/sympy/solvers/solvers.pyc in
solve(f, *symbols, **flags)
885
###########################################################################
886 if bare_f:
--> 887 solution = _solve(f[0], *symbols, **flags)
888 else:
889 solution = _solve_system(f, symbols, **flags)
/usr/local/lib/python2.7/dist-packages/sympy/solvers/solvers.pyc in
_solve(f, *symbols, **flags)
1356 poly = Poly(poly.as_expr(), poly.gen,
composite=True)
1357 soln = list(roots(poly, cubics=True,
quartics=True,
-> 1358
quintics=True).keys())
1359
1360 if len(soln) < deg:
/usr/local/lib/python2.7/dist-packages/sympy/polys/polyroots.pyc in
roots(f, *gens, **flags)
880 _update_dict(result, root, 1)
881 else:
--> 882 for root in _try_decompose(f):
883 _update_dict(result, root, 1)
884 else:
/usr/local/lib/python2.7/dist-packages/sympy/polys/polyroots.pyc in
_try_decompose(f)
783 factors, roots = f.decompose(), []
784
--> 785 for root in _try_heuristics(factors[0]):
786 roots.append(root)
787
/usr/local/lib/python2.7/dist-packages/sympy/polys/polyroots.pyc in
_try_heuristics(f)
829 result += roots_cubic(f)
830 elif n == 4 and quartics:
--> 831 result += roots_quartic(f)
832 elif n == 5 and quintics:
833 result += roots_quintic(f)
/usr/local/lib/python2.7/dist-packages/sympy/polys/polyroots.pyc in
roots_quartic(f)
291 y = -5*e/6 + u - p/u/3
292 else:
--> 293 raise PolynomialError('cannot return general
quartic solution')
294 w = sqrt(e + 2*y)
295 arg1 = 3*e + 2*y
PolynomialError: cannot return general quartic solution
-------------------------------------------------------------------------------
I tried to solve the same equation in WolframAlpha and SAGE, there are
solutions in both systems, only SymPy gives this error.
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