√x + √y + √z = 4 .. Answer Please.Solve for x, y, z

There is no single answer.

For instance:  x = 16, y = 0, z = 0

                    x = 4, y = 4, z = 0

                    x = 25/9, y = 4, z = 1/9

etc. 

There is an infinite number of possible answers.