Positioned inside the framework of linear and exponential functions, this lesson is more of an investigation into the effects of changing variables and constants inside an expression. The author takes familiar formulas, those for triangle perimeter and compound interest, and teases out how changing variable values influences overall expression results while leaving other individual parameters unchanged. Applets built around the specific examples in the lesson give some concrete meaning to the abstract questions and answers and turn this presentation into a hands-on math experiment.