This lesson marks students’ first encounter with the number . Students are not expected to construct exponential functions with base , and understanding in depth is beyond the scope of this course. Students are, however, expected to be able to interpret and graph such functions using technology. They will also return to logarithms as a way to solve exponential equations with base , relating back to earlier work.

In the first activity, students notice the letter being used as the base of an exponential function with a growth factor of about 2.7 and learn some basic facts about the mathematical constant. Next, they investigate the behavior of some functions for certain values of input and observe some patterns emerging (MP8). They notice that a particular expression, , is closely related to the value .