This lesson discusses how to use the average rate of change to estimate the instantaneous rate of change, leading up to using the difference quotient to figure out exacly what the instantaneous rate of change is. Please note at the 10:32 mark, I made a slight error by writing "2+t" when I meant to write "2+h"; I realized it about 30 seconds later and corrected but just wanted to let you know in advance to avoid any confusion!! :)