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Wrong Answer?

asked 2014-08-19 16:46:36 -0600

When I ask Sage to solve a simple rational inequality it occasionally gives a wrong answer. For example, $$ \frac{x^2 - 9 }{x-3} \geq 0$$ is satisfied when $x \geq -3$ except at $x=3$, but Sage just gives $x \geq -3$. Here's the code I am using:

sage: solve((x^2-9)/(x-3) >= 0,x)
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answered 2014-08-20 07:50:12 -0600

kcrisman gravatar image

updated 2014-08-21 15:20:10 -0600

This is in Maxima.

Maxima 5.33.0 http://maxima.sourceforge.net
using Lisp ECL 12.12.1
Distributed under the GNU Public License. See the file COPYING.
Dedicated to the memory of William Schelter.
The function bug_report() provides bug reporting information.
(%i1) load("solve_rat_ineq"); 
(%o1) /Users/.../sage/local/share/maxima/5.33.0/share/solve\
_rat_ineq/solve_rat_ineq.mac
(%i2) solve_rat_ineq((x^2-9)/(x-3) >= 0);
(%o2)                            [[x >= - 3]]

That said, Maxima (and Sage and lots of other things) do simplify x^2/x to be just x, so I am not 100% sure it's not intended behavior. Anyway, I agree it would be better to not have the 3, so I've reported it at Maxima bug 2804.

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Asked: 2014-08-19 16:46:36 -0600

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Last updated: Aug 21 '14