Students sort functions and non-functions shown in tables, graphs, equations and ordered pairs onto a Venn diagram. The "inner circle" of the Venn diagram is where functions go as functions are always relations but relations are not always functions. The relations that are not functions go in the part of the Venn diagram labeled "relations". This is a good introduction to what it means to be or not to be a function. This activity works great as an introduction to functions, as a warm up after a lesson on functions, as a closer or as part of an interactive notebook.
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