The exercise is appropriate for pre-calculus or beginning calculus students. This is a cooperative learning exercise. Each student is given a function definition and asked to graph the function, and then to write a non-mathematical description of the appearance of the function. Students form pairs, with each partner having the same function. The partnership refines the written description, and signs it.
Pairs attempt to find the function that fits the description.
This may be an iterative process. When a pair proposes a function, the description writers may respond You've got it. That can't be the function because it doesn't satisfy a particular aspect of the description. Additional rounds give the students practice matching functions to descriptions. Prerequisites will vary depending on the functions used.