I would like to evaluate the properties (positive/negative) of a non-numerical solution. Is it possible to define a variable as a range of values (no as a plot) and is it possible to create binary solutions?

A mathematical example:
0<a<1,
0<b<1,
a+b>1.
x = a(1-b)(1-a-b) < 0
I would like to assign +/i signs for the function and solution such as (+)(+)(-) and therefore (-).

Thank you in advance!