Dividing [6,9] by (-3,0) obviously will yield an
interval of (-Infinity,-2), but what about [6,9]
divided by (-3,0]? With the zero endpoint included in
the range, the correct answer should be something like
"(-Infinity,-2) U Infinity", but there is currently no
way to represent that properly.
Similar problem occurs when dividing by (0,b) vs [0,b).
This is further complicated by the fact that the zero
endpoint may actually be "negative zero", which is the
subject of another issue.
