About 3.606, if you round it.
This expression is easier than it looks like. I thought that to solve it you have for example to express the 2 via 10 * 5^-1 and stuff like that - but you can multiply and divide this expression by some factor. In our case first we multiply by conjunctive expression root(5-2root2) and the second by root(6+2root5). In first we get root16 and the second calculate.
The answer to your question is (x^ 2) - 4
