Resolved: quadratic-equation has been made a synonym of quadratics.
We have two tags quadratics and quadratic-equation. I think they should be synonyms. (I do not have sufficient reputation in either of the two for suggesting a synonym.)
The tag-wikitag-wiki of the first one specifically says that it is for questions about quadratic equations. The second one has empty tag-wiki, but the name of the tag is self-explanatory. So does the second one.
Tag-excerpt history for quadraticsfor quadratics, tag-excerpt history for quadratic-equationsfor quadratic-equations, tag-wiki history for quadratic-equationsfor quadratic-equations. (I have added these links to preserve the tag-excerpts/tag-wikis; since it is difficult to find them once the tag has been removed.)