Emma throws an object upward from a hill that is 64 feet high. The object has an initial velocity of 48 feet per second. The function y = -16x2 + 48x + 64 represents the height of the object, y, in terms of the time elapsed after the object is thrown, x. Which statements about this function are true? The function is a linear function. The function is a nonlinear function. The function has a constant rate of change. The function does not have a constant rate of change. The function is a decreasing function.