More with Adding and Subtracting Polynomials

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SWBAT add and subtract polynomial expressions.

Big Idea

This lesson allows students to work together in a cooperative structure to simplify polynomials and justify their reasoning.


12 minutes

Slide 1

I have students work in pairs on the first part of the add_polynomials2_warmup.  Students will have to understand what this problem is asking them to find MP1.  They will also need to examine the structure needed to have the given polynomial represent the perimeter MP7.   I give students  about 3-4 minutes to make their sketches.  Next, I choose several pairs of students to justify their sketches to the class using either the board or a document camera (MP3). As they present, I give other members of the class an opportunity to ask questions.

Slide 2

When we transition to the second slide, I have students think about the difference between this question and the first question (MP1).  I begin by having students share ideas with a partner and as they develop a plan to solve the problem.  Then, I allow each partnership to carry out their plan.  Afterward, I ask 1 or 2 pairs share their responses and I allow the class to ask questions. Students should try to determine if the solution could represent the sides of a rectangle with the given perimeter.

Cooperative Practice

20 minutes

This activity is called Numbered Heads Together.  Each student is given their own dry erase board.  Each student in each group is assigned a number 1-4.  The objective is to have all four students work together on each of the nine problems in this section.   The problems are given one at a time.  

I give students approximately 2 minutes to work on each problem.  At the end of two minutes I choose a number: 1, 2, 3, or 4.  (For this I have used index cards numbered 1-4 or you can use an online random number spinner - students tend to like this better!).  Whichever number comes up is the student who needs to show their work for the group. This students work is the the only work that counts for the group.  I award points to groups with correct answers, or for making a lot of progress, or showing the most perseverence, etc.

I like this activity because:

  • The format encourages students to work together due to the random accountability.
  • Students need to discuss their ideas MP3 and be critical about which ideas they accept to put down as the group solution.  I always enforce the requirement that whichever number comes up, the student must be able to explain his/her answer. This practice dissuades students from copying one another.  
  • In this activity, students will need to look at each question as a "mini" problem or exercise that the group needs to understand and to make a plan to solve (MP1).  



8 minutes

The add_polynomials2 ticket out the door requires students to reason abstractly about polynomials (MP2).  I encourage students to explain their ideas for Question 2 as thoroughly as possible.  They can use examples to explain their thoughts to make their argument more easily understood (MP3).  If time permits, I allow students to swap papers with their partners so that partners can give each other feedback before handing in their exit ticket.