Chapter 9 - Quadratic Functions and Equations - 9-1 Quadratic Graphs and Their Properties - Practice and Problem-Solving Exercises - Page 550: 30

Domain: All real Numbers Range: y $ \leq -1$

For a parabola, the domain is almost always all real numbers. We see that at the vertex, the value of y is -1. Since $-2x^2$ will mean that the function will be pointed downwards, the vertex is the maximum value of the range.