I'm trying to solve some equations in mathematica and need to make some assumptions about the variables e.g. x is positive. I'm not sure how to do this. As a simple example I tried
Assuming[x > 0, Simplify[Solve[x^2 == 9, x]]]
expecting to just get the output x=3. However, mathematica gave me the output x=3 and x=-3. How do I get it to solve this equation with x restricted to positive values?