I have, for $6n$ real variables, a system of O$(n^2)$ inequalities over the reals. $n$ of these are linear, while the rest are quadratic. How do I determine that for some $n$
- a solution exists,
- and if it does, what is the solution set?
I am looking for the algorithms with the best possible computational complexity. For (2) I will even be happy with finding one solution if doing so is faster than finding the solution set. What are some methods to do this?
If codes already exist for these methods I will appreciate links.