x=√2+√2-√2+x value of x
Please state this problem more carefully. I suspect that you may mean something like x=√{2+√[2-√(2+x)]}, or $\displaystyle x = \sqrt{2+\sqrt{2-\sqrt{2+x}}}.$ Even then, the problem does not make much sense unless the – sign in the middle of that expression should be a +.