Status: Valid
Owner: ----
Labels: Type-Defect Priority-Medium Concrete EasyToFix WrongResult
New issue 3565 by [email protected]: Sum(x**n, (n, 0, oo)).doit() is wrong
http://code.google.com/p/sympy/issues/detail?id=3565
In [24]: Sum(x**n, (n, 0, oo)).doit()
Out[24]:
∞
- x + 1
────────
-x + 1
The answer should be 1/(1 - x) (or actually, a piecewise of that when |x| <
1 and the summation otherwise). I don't see how the hypergeometric
algorithm wouldn't apply to this. The issue is probably that the finite
geometric series summation formula hits it first and it never gets to that
part of the code. If that's true, this should be easy to fix (just make
sure that part of the code checks the limits for finiteness).
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