CAS command question

[parisse]

Symbolic expressions are rewritten with fewer operators during evaluation because after that it's easier to handle less operators. The same happens with substraction or division: if you enter c:=a-b or c:=a/b it is evaled to a+neg(b) or a*inv(b) : try c[1] (you won't see on the display because it is easy to check that. But it is impossible to do the same for inequations, since the user could have entered 2<x or x>2).
If you are playing with symbolic expressions, you must always keep this in mind. It may look like conter-intuitive, but once you know that, your programmer task will be easier, because you won't have to handle < or <= or binary - or /