Graphing Radical Functions

The function $y=\text{-}2\sqrt{x}$ is a radical function with an even index. Since the function doesn't have any added/subtracted constant, it will start on the $x$-axis where $y=0.$ The radicand will always give a positive answer and since the coefficient is negative the $y$-values will only be negative.

Thus, the range is $y \leq 0.$