Graphing y=1/x

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Students will graph the function y=1/x. Students will use the concept of infinity to describe the behavior of this function and identify the asymptotes of this function.

Big Idea

Use silly, exaggerated division problems to understand the behavior of the function y = 1/x. Make arguments involving 0 and infinity.


30 minutes

Investigation and New Learning

30 minutes
Investigation Narrative.docx page 1


10 minutes

At this point, once all students have completed a graph of the reciprocal function and can explain its behavior, I will give them some information about the two concepts above. The document below introduces two key questions about the graph, which will turn into approach statements. These approach statements are a precursor to limits, which is geared towards preparing students for calculus.

I use Exit Ticket #3. I let students guess at the approach statements first. They will probably guess very incorrectly, because these are really abstract and new for them. This is their first early exposure to it, so the point is just to get them started thinking about it. (Don’t be worried if none of them seem to understand these at this point. They will understand them over time.) For today, the key questions are what is essential. So, I take 5-10 minutes to go over the new inputs on this page, then have students answer the exit ticket questions.

During this segment of the lesson, you can choose whether or not you want to provide direct instruction about approach statements. At most, I would present to students the answers to the questions in the approach statements document, and take the time to show how the answers appear in the graphs and in the data tables. Eventually, these will connect to the asymptotes and students will make generalizations about them, but for now just looking at the graph and data table will be concrete and clear to most students.