2.8 is greater than 2.78 because 2.8 would basically be 2.80 so you can just add 0 at the end cause that wouldn’t change anything. So 2.80 you can see is greater than 2.78 because .80 > .78 Hoped this helped!
Like the cubic term -3x^3 is negative, for small values of "x", the dependent variable "y" will rise. All this can be verified by looking at the graph.