Status: New
Owner: ----
Labels: Type-Defect Priority-Medium

New issue 1410 by smichr: solve doesn't factor out a common exponential  
from system of equations
http://code.google.com/p/sympy/issues/detail?id=1410

On the sympy list someone posted the folowing failure of solve:

>>> La derivata prima in x: (a)
>>>                   x*y x*y
>>> - y*(3 - x - y)*e + e
>>> La derivata prima in y: (b)
>>>                   x*y x*y
>>> - x*(3 - x - y)*e + e
>> ...
>>> I punti critici sono:
>>> Traceback (most recent call last):
>>> File "E:\unico_2.py", line 36, in <module>
>>> p = sympy.solve([a, b], [x, y])
>>> File "C:\Python25\Lib\site-packages\sympy\solvers\solvers.py", line
>>> 272, in solve
>>> raise NotImplementedError()
>>> NotImplementedError

The exponential terms factor out (and cannot equal 0) so the system is
easily solvable once that factor is removed:
>>> solve([1-y*(3-x-y),1-x*(3-x-y)],[x,y])
[(1/2, 1/2), (1, 1)]


The solver needs to see if there is a common factor that can be
removed and solved (or not solved in this case) before solving the
remaining residues:[F(x,y)*G(x,y), F(x,y)*H(x,y)] can equal zero if
F(x,y)=0 and when both G(x,y) and H(x,y) are zero.

/chris



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