Math 1 · Unit 2 · Lesson 3
Domain and Range: The Inputs and the Outputs
Domain is the inputs, the x values a function is allowed to take. Range is the outputs, the y values that come out. Find them from a table, from a story (time cannot be negative, you cannot have half a person), and by reading the edges of a graph. Write them in words or as an inequality.
The big idea
Every function has two piles of numbers: the inputs it takes, called the domain, and the outputs it gives back, called the range. With a plain rule and no story, both piles are usually all numbers. A story shrinks them to what makes sense: time starts at zero and stops when the story ends, people come in whole numbers, a stadium fills up. A graph shows both piles at a glance: read left to right along the bottom for the domain, bottom to top along the side for the range. Write the answer in words or as an inequality, and say whether the values are connected or a list of separate ones.
The parts of this lesson
Each part is its own short page. Go in order, or pick the one you need.
Printables
One page with both words, the three story examples, how to read a graph, and a worked reasonable domain and range. Plus a worksheet with an answer key and a short lesson plan.