Describe how the graph of y = −4x2 differs from the graph of y = −x2 . a. the graph of y = −x2 is narrower than the graph of y = −4x2. b. the graph of y = −4x2 is narrower than the graph of y = −x2. c. the graph of y = −4x2 is the same as the graph of y = −x2 but shifted down by 4 units. d. the graph of y = −4x2 opens upward while the graph of y = −x2 opens downward.