sqrt(x).is_negative returns False instead of None

[Smit-create]

Fixes sqrt(x).is_negative to return False instead of None

References to other Issues or PRs

Fixes #14815

Brief description of what is fixed or changed

Before fixing:

>>> from sympy import Symbol, sqrt
>>> x = Symbol('x')
>>> sqrt(x).is_negative
>>>

After fixing:

>>> from sympy import Symbol, sqrt
>>> x = Symbol('x')
>>> sqrt(x).is_negative
False

Other comments

Release Notes

• core
  • sqrt(x).is_negative is False when x is real

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• core
  • sqrt(x).is_negative is False when x is real (#18597 by @Smit-create)

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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. -->
Fixes `sqrt(x).is_negative` to return `False` instead of `None`
#### References to other Issues or PRs
<!-- If this pull request fixes an issue, write "Fixes #NNNN" in that exact
format, e.g. "Fixes #1234" (see
https://tinyurl.com/auto-closing for more information). Also, please
write a comment on that issue linking back to this pull request once it is
open. -->
Fixes #14815

#### Brief description of what is fixed or changed
Before fixing:
```
>>> from sympy import Symbol, sqrt
>>> x = Symbol('x')
>>> sqrt(x).is_negative
>>>
```
After fixing:
```
>>> from sympy import Symbol, sqrt
>>> x = Symbol('x')
>>> sqrt(x).is_negative
False
```

#### Other comments


#### Release Notes

<!-- Write the release notes for this release below. See
https://github.com/sympy/sympy/wiki/Writing-Release-Notes for more information
on how to write release notes. The bot will check your release notes
automatically to see if they are formatted correctly. -->

<!-- BEGIN RELEASE NOTES -->
* core
   * `sqrt(x).is_negative` is False when `x` is real
<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[oscarbenjamin]

This should be applied to extended_negative rather than is_negative.

[Smit-create]

Okay, will change that

[oscarbenjamin]

If we return None for nan/zoo than we have to also return None for a plain Symbol('x').

[Smit-create]

If we return None for nan/zoo than we have to also return None for a plain Symbol('x').

But from #14815(comment) i.e in orginal issue was to return False for Symbol('x').

[oscarbenjamin]

It would be good to have a test for a symbol with complex=True and another with extended_real=True.

[asmeurer]

is works here because 1/2 is singletonized, but it's generally better to be explicit about that and use S.Half if you are using is (otherwise use ==).

[asmeurer]

We should be able to generalize this.

[Smit-create]

Okay I would change that and keep it correct next time. Should I commit this to same branch?