diophantine: note re parametric soln; remove gcd

[smichr]

References to other Issues or PRs

closes #11697

Brief description of what is fixed or changed

A docstring has been updated to indicate the relationship between the parameterized solution and the actual solution: the parameterized solution does not produce coprime results from coprime input.

I also noticed that symbolic gcd was not being handled so updated the routine that removes the gcd of parameterized solutions.

Other comments

Release Notes

• solvers
  • the gcd of parameterized ternary solutions is now removed

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• solvers
  • the gcd of parameterized ternary solutions is now removed (#17348 by @smichr)

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#### References to other Issues or PRs
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closes #11697 

#### Brief description of what is fixed or changed

A docstring has been updated to indicate the relationship between the parameterized solution and the actual solution: the parameterized solution does not produce coprime results from coprime input.

I also noticed that symbolic gcd was not being handled so updated the routine that removes the gcd of parameterized solutions.

#### Other comments


#### Release Notes

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https://github.com/sympy/sympy/wiki/Writing-Release-Notes for more information
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<!-- BEGIN RELEASE NOTES -->
* solvers
    * the gcd of parameterized ternary solutions is now removed
<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[smichr]

Unless there are suggestions for changes I plan nothing else for this.

[codecov]

Codecov Report

Merging #17348 into master will increase coverage by 0.088%.
The diff coverage is 100%.

@@              Coverage Diff              @@
##            master    #17348       +/-   ##
=============================================
+ Coverage   74.603%   74.692%   +0.088%     
=============================================
  Files          627       631        +4     
  Lines       162864    163167      +303     
  Branches     38214     38282       +68     
=============================================
+ Hits        121503    121874      +371     
+ Misses       35979     35959       -20     
+ Partials      5382      5334       -48

[jksuom]

Edited release note entry.

[jksuom]

Is the extra indentation necessary?

[smichr]

My feeling was that this is more of a parenthetical comment and I wanted it to appear as such. Perhaps putting it under Notes would be better?

[jksuom]

That might be better unless the presence of examples will confuse Sphinx.

[jksuom]

This should clarify the nature of the parametrization, pointing out that primitive solutions are not necessarily among those parametrized by integers.