In this clip the teacher leads a discussion about what makes a situation exponential.
Introduction to Exponential Functions, Clip 2, 3:15
The teacher does a nice job of getting the students to talk about what it means to double something. While this concept is not difficult for the students, it will give her an opportunity to establish a normative way of discussion how the base of an exponential function works. In this case they look at doubling as repeated multiplication by 2.
Notice how the teacher extends the discussion until they phrase doubling in terms of repeated multiplication by 2 and then recaps the student's answer for the other students. Again, this will help establish a way of talking about exponential behavior and factors.
In this case the teacher also uses this disucssion to segue into a discussion of what the formula would look like it it doubles every 5 squares. This is an opportunity for students to explore double time.
