Since you squared both sides (twice in this case), you have the potential of having introduced an extraneous root. Therefore, check the answer:
The root is extraneous and there was only one root, so the solution set is the empty set. Now, look back at the step I pointed out to remember. 4 is a positive number and is a positive number because an unsigned even-indexed radical is defined as the positive root. Since a positive number multiplied by a positive number is positive, such a product cannot be equal to a negative number, specifically -20. Therefore, we could have quit at this step because it is clear that the equation has no solution.
John
My calculator said it, I believe it, that settles it
