The domain is
The general procedure with such a type of equation is:
Square both sides - isolate remaining roots at one side - square again - isolate ... and so on:
...... Square again:
...... Collect like terms:
I don't know how to solve such an equation algebraically. So I used my computer which calculated 4 approximate solutions:
Since squaring is not an equivalent operation you must check these values by plugging them into the original equation and check if they satisfy the equation.
Better use a calculator