In this lesson, students focus their attention on possible input and output values. They define the list of possible inputs as the domain of the function and the possible outputs as the range of the function. They identify the domain and range of functions from graphs and descriptions of situations, then describe them using words, lists of numbers, or inequalities (if appropriate).

Students' analyses of inputs and outputs continue to be grounded in context, allowing many chances to reason quantitatively and abstractly (MP2). In an optional activity, there is an opportunity to study the domain of a function without a context.