sympy/sympy — pull request #1616 by smichr (2012-10-27 09:51:42+00:00)
Title: WIP 3460: watch for oo in ndiv

By watching for extractable negatives at the outset, the
problem can be circumvented. I'm not sure where the infinities
are being generated by such a simple substitution as
(-12*x).subs(-x,1).