Question 1013064
There is nothing special about negative coordinates.
They are negative because we set a zero in an arbitrary place,
and arbitrarily decided to what side of that zero we would call the numbers negative numbers.
Your negative numbers are not negative if you set the zero far enough to the negative side.
You can move the coordinate axis so that every coordinate you are using is positive, and the distances and relative positions from one point to another will not change.
You could even flip one or both axes around to point in the opposite direction, and distances and relative positions of those points would not change.
 
Why the formula is like that is a different story.