And so that's why the slope of the secant line is the average rate of change. Is it the exact rate of change at every point? Absolutely not. The curve's rate of change is constantly changing. It's at a slower rate of change in the beginning part of this interval, and then it's actually increasing at a higher rate as we get closer and closer to three. So over the interval, their change in y over the change in x is exactly the same. Now one question you might be wondering is, why are you learning this in a calculus class?