##
* *Reflection:
Function Notation - Section 4: Closure

The investigation for this lesson went very smoothly because it allowed students to refine their thinking from the previous lesson. I was actually surprised how many students had made a table during their investigation of the tower task from the previous lesson. Based on that work, the students were able to use their table to construct a graph of their function.

We had a very good dialogue around whether or not the points should be connected on the graph. As I was monitoring student work, I noticed that most students had connected their points before reading the prompt regarding whether or not to connect them. **The next time I teach this lesson I will call attention to this prompt first so that it is in the back of students minds.** Once students reflected back on the inputs and outputs, they decided that the graph could be made up of a series of points that are not connected. However, we also said that the function used to model this graph f(x) = 5x - 4, would be a line. The students also made some interesting observations regarding the slope of the line and the rate of change in the problem. Students noticed that since 5 blocks were being added each time the slope of the line would be 5.

The video portion of the lesson also went well. I am currently in the process of "flipping" some of my lessons. So, I used this video as an opportunity to teach students how to watch a "math" video (since this is what they would be doing at home). I explained to them that they would need to stop the video in order to process, or predict or write something down. I had one of my students, Javonne, take control of the video and I asked her to pause whenever she felt there was something important to write down. She stopped at nearly all of the prompts that I had planned which worked out very well. It also showed me that students have some good insight into the important points in an instructional video.

From the video, students were able to work on the closing activity. This gave me some very good insight into student's preliminary understanding of evaluating functions. I was happy to see that most students used a calculator to help them with the evaluation so the emphasis was on the input/output and not the arithmetic. Students did not get bogged down with the input/output notation (ex f(3)=8) they knew that they had to plug in 3 for x and that the answer would either be 8 or something else. If the answer was something else then the original equation would be false. As you can see from the student work (I chose three levels of students since all of the student work was basically correct) they seemed to have a good understanding of the content.

# Function Notation

Lesson 4 of 18

## Objective: SWBAT evaluate functions written in function notation. SWBAT determine if a relation is a function based on the input and output values.

#### Opening

*5 min*

Students will get back into their groups from the previous lesson and revisit the tower task. My directions for students are to: (1) Discuss the recursive formula that you determined for the tower task and why it works. (2) Discuss the explicit formula that you determined and why it works. (3) Name one thing that you saw on another groups chart that stuck with you. Opening in this way serves to reframe the conversation and get all members of the class back up to speed with where they had left off the day before. I go around to each group and have them share out one of the three items (I choose which item will be shared in order to hold all groups accountable and to ensure that each topic gets proper treatment).

*expand content*

#### Investigation

*15 min*

Students work in their groups to extend and organize their thinking from the tower task. In completing this work the groups are learning how to use multiple representations to display the same idea (algebraically, graphically, numerically in a table).

**What to watch out for:**

**-**Watch to see that each group is evaluating the equation B = 5H – 4 ** **at each value of H. The step is crucial in understanding how to evaluate functions later on in the lesson. If groups are merely coping both sides of the table and leaving the center column blank, encourage them to validate their answers by evaluating the equation at each point.

-The “think” question that goes along with the graph was included very intentionally here. While students have not really been exposed to discrete data in middle school it is important that they start to think about the domain and range of the function in terms of the context it describes. The decision of whether or not to include the words “domain” and “range” in this lesson can be made based on student dialog around this particular question.

-Students may need some guidance on the term “rate of change.” While this term is used very heavily in the eighth grade standards, you may need to revisit this concept either with individual students or, if necessary, with the whole class.

Once each group has a chance to work through all of the prompts on the investigation, I bring the whole class together to discuss the “think” question and the “rate of change” question. When I structure a whole class discussion like this, I like to create an environment where after one person shares, each subsequent person should try to build off of and add to the initial idea. This forces the students to listen to each other and not just wait for their turn to share their own idea. It is only when we have exhausted an idea that we move on and start another thread with a new idea.

*expand content*

#### Direct Instruction

*20 min*

We have now been using the word function for several days. The next portion of the lesson is going to tie a few concepts together and uses the tower task as the common thread. I show the following video and while students are watching I stop the video at certain times so that students can do a **think-pair-share** with one other member of their group. Stop times and good questions to ask are shown below:

0:54-In the tower task, what is the input and what is the output?

2:57-Let students know that *f* and *g* are not the only names for functions. Any letter can stand for a function.

3:20-Pause video here and ask students to explain to their partner where the 26 and the -9 came from to ensure they are understanding the evaluation step.

-How could we use function notation to write the following: How many blocks does it take to build a tower that is 5 blocks tall? (This may need to be shared out whole class so that students can see that it can be written as either *B(5) = 5(5) – 4 *or* f(5) = 5(5) – 4.*

* *

6:05-Ask students to look back at the table that they filled in for the tower task and their answer to “is this relation a function?” Have them discuss whether or not their answer is correct based on this definition or if they need to change their answer. Give an opportunity for groups to share out as needed so that all students are convinced that the tower task is a function.

8:17-Ask students to look at the graph that they created. Does this graph pass the vertical line test?

*expand content*

Hi Kelly. When I use the video link it plays without requiring any kind of subscription. Send me an email directly at bialasikj@gmail.com and I can try to send you another link.

| 3 years ago | Reply

The functions video requires a $49.99/month fee to maintain access. There is a 5 day free trial but one has to enter credit card information to get that trial started. Is there another video you would recommend that s free?

| 3 years ago | Reply##### Similar Lessons

###### Graphing Radical Functions Day 2

*Favorites(2)*

*Resources(7)*

Environment: Suburban

###### The Function Game

*Favorites(16)*

*Resources(9)*

Environment: Suburban

Environment: Urban

- LESSON 1: PRE-ALGEBRA: Evaluating Expressions
- LESSON 2: Defining Functions Recursively
- LESSON 3: Tower Task: Exploring Explicit Formulas
- LESSON 4: Function Notation
- LESSON 5: Understanding Domain and Range
- LESSON 6: Multiple Representation of Functions
- LESSON 7: Piecewise and Step Functions
- LESSON 8: Mirror Task: Understanding Equivalent Functions
- LESSON 9: Modeling with Functions
- LESSON 10: Functions Practice and Assessment
- LESSON 11: Introduction to Piecewise Functions: Dance-a-Thon Question
- LESSON 12: More with Piecewise Functions
- LESSON 13: Evaluating Functions Day 2
- LESSON 14: Transformation of Functions Day 1
- LESSON 15: Transformation of Functions Day 2
- LESSON 16: Transformations "How To" Guide
- LESSON 17: Functions Review Assignment
- LESSON 18: Functions Unit Assessment