Can I put restrictions on possible values for variables?

Say I have a system of equations or an equation I want to solve, but only under certain conditions for my variables (eg: x is not 0 or x<20)

How could I create a variable with certain restrictions on it's possible values? (or would I specify that when using a specific function for solving the equation(s)?

Side note: I'm not quite sure how I will solve the equation(s) but I may use one of the following: http://www.mathworks.com/help/symbolic/solve-a-system-of-algebraic-equations.html http://www.mathworks.com/help/symbolic/mupad_ref/linsolve.html http://www.mathworks.com/help/symbolic/solve.html

Answer 1

[Star Strider]

I’m not certain what you are doing, but the Symbolic Math Toolbox assume function (and its friends listed at the end of the page) may be helpful.