In this clip the students are solving an equation in which the exponent is unknown.
Introduction to Logarithms, Clip 3, 4:08
The students are familiar with the exercise of "taking the log of both sides", but the teacher requires them to justify why they can do this. It is important that students understand why this works.
It can often be necessary for the teacher to push students to create appropriate justifications for their conjectures. Often times when they are trying to justify, misconceptions may come out that the teacher can then address. In this case, that log is a variable.
