Modeling Rational Functions

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Objective

Students will be able model and graph rational functions.

Big Idea

Analyze the contextual meaning and properties of the graph of a rational function in this modeling lesson.

Warm up and Homework Review

10 minutes

I include Warm ups with a Rubric as part of my daily routine. My goal is to allow students to work on Math Practice 3 each day. Grouping students into homogeneous pairs provides an opportunity for appropriately differentiated math conversations. The Video Narrative explains this lesson’s Warm Up- Modeling Rational Functions which asks students to describe a situation where the domain of a function is not all real numbers.    

I also use this time to correct and record the previous day's Homework.  

Modeling Rational Functions

23 minutes

The goal of this lesson is to introduce students to the graphs and equations of rational functions by modeling real life situations (Math Practice 4).  We begin with a problem on splitting the bill at a restaurant.  Through this scenario, the students get an opportunity to investigate the domain, range, intercepts (or lack of intercepts) and asymptotes (Math Practice 2).   This is run as a guided investigation.  I pose a question to the students, have them discuss it with their partner, and then we discuss it as a class.  Please read the amazing article on running effective classroom discussions. 

The scenario then changes twice, once using a vertical translation and then a horizontal translation.  The students compare the features of these graphs to the features of the original graph (Math Practice 7).

Please see the PowerPoint for detailed presentation notes.

Modeling Inverses of a Rational Function

15 minutes

The next scenario involves splitting the cost of a Gift.  We look at the inverse of this problem in addition to the general features introduced in the last scenario.  This one is particularly interesting because the function and its inverse are equivalent.  Referring the functions back to how they represent the scenario makes this activity richer.   

Exit Ticket

2 minutes

I use an exit ticket each day as a quick formative assessment to judge the success of the lesson.  

Today's Exit Ticket asks students to list three things that they learned from the day’s lesson.

Homework

This assignment presents the students with a new rational function scenario, asks them to model it, and then use the model to gain information about the scenario (Math Practice 4).  The goal is to give students practice with modeling outside of the classroom environment.