which is certainly true enough and indicates that the answer is valid, but only to the extent that there are no restrictions on the value of the variable in your original equation such that the equation must always be defined in the real numbers. Your original equation is undefined in the reals for any value of because the radicand on the right would then be < 0.
Consequently, your solution set either contains the single value if there are no restrictions on the value of x or is the empty set if x is restricted.
