select minpoly from factors

[smichr]

closes #26903

References to other Issues or PRs

Brief description of what is fixed or changed

A check that the number is not trivially 0 before starting removal of square roots is now done. If it is not done, then -x**2 can be returned from the _separate_sq helper (which is only called from _minpoly_compose).

Other comments

Release Notes

• polys
  • fixed minpoly to not return -x**2 instead of x for an unsimplified value of 0 comprised of a difference of square roots

[sympy-bot]

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• polys
  • fixed minpoly to not return -x**2 instead of x for an unsimplified value of 0 comprised of a difference of square roots (#26919 by @oscarbenjamin and @smichr)

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<!-- Your title above should be a short description of what
was changed. Do not include the issue number in the title. -->
closes #26903

#### References to other Issues or PRs
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#### Brief description of what is fixed or changed

A check that the number is not trivially 0 before starting removal of square roots is now done. If it is not done, then `-x**2` can be returned from the `_separate_sq` helper (which is only called from `_minpoly_compose`).

#### Other comments


#### Release Notes

<!-- Write the release notes for this release below between the BEGIN and END
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* solvers
  * Added a new solver for logarithmic equations.

* functions
  * Fixed a bug with log of integers. Formerly, `log(-x)` incorrectly gave `-log(x)`.

* physics.units
  * Corrected a semantical error in the conversion between volt and statvolt which
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<!-- BEGIN RELEASE NOTES -->
* polys
  * fixed minpoly to not return `-x**2` instead of `x` for an unsimplified value of 0 comprised of a difference of square roots
<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[github-actions]

Benchmark results from GitHub Actions

Lower numbers are good, higher numbers are bad. A ratio less than 1
means a speed up and greater than 1 means a slowdown. Green lines
beginning with + are slowdowns (the PR is slower then master or
master is slower than the previous release). Red lines beginning
with - are speedups.

Significantly changed benchmark results (PR vs master)

Significantly changed benchmark results (master vs previous release)

Full benchmark results can be found as artifacts in GitHub Actions
(click on checks at the top of the PR).

[oscarbenjamin]

Looks good. Thanks