We discussed the question, "What is the fundamental difference between x3 and x2?" We decided that in speaking about how they changed differently, we really needed to talk about their respective rates of change. For example, x3 changes more slowly than x2 between 0 and 2/3, and it changes more rapidly than x2 for x > 2/3. We devised a method for estimating rates of change of a function with the function g(x) = (f(x+h) - f(x))/h, where h is a parameter.