Add and Subtract Linear Expressions

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Objective

Students will be able to add and subtract linear expressions.

Big Idea

A step further than simple combining like terms – now parenthesis are involved, but with the right moves, it is just as easy!

Launch

10 minutes

Opener:  As students enter the room, they will immediately pick up and begin working on the opener.  Please see my instructional strategy clip for how openers work in my classroom (Instructional Strategy - Process for openers).  This method of working and going over the opener lends itself to allow students to construct viable arguments and critique the reasoning of others, which is mathematical practice 3.  

Learning Target:  After completion of the opener, I will address the day’s learning targets to the students.  In today’s lesson, the intended target is, “I can add and subtract linear expressions.” Students will jot the learning target down in their agendas (our version of a student planner, there is a place to write the learning target for every day). 

                  

Explore

50 minutes

Add and Subtract Linear Expressions Notes:  Today’s topic builds off of yesterday’s lesson on combining like terms.  Therefore, to start today’s lesson, I am going to address how to make these problems look just like the ones we did in the previous lesson, by going over a few notes.  For addition, I will show the students that we can just drop the parenthesis and combine like terms.  For subtraction, there is an added step, but it is just as easy!  I will ask students to tell me what we did when we subtracted integers – we added the opposite – which is exactly what we will do here.  I am going to have the students change the subtraction sign to addition, and then change the sign of each term to its opposite, drop parenthesis and combine like terms.  Students will need to pay close attention to precision, so that they are combining terms correctly (mathematical practice 6).  I will model a couple of problems by thinking aloud and bringing students into the conversation.  What operation is this? What should I do? What are my like terms?  After a couple of examples, I will do one additional example by lining up the expressions vertically.  For some students, this is an easier way to organize the like terms, as adding and subtracting vertically is a natural flow from how they were originally taught to add and subtract.

Table Practice: With their tables, students are going to work on 6 example problems.  We have done 3 together as a class, so I am going to ask that students work and struggle (persevering with problem solving mathematical practice 1) as a group to come up with the correct answers.  Students know that I will help them if they really need it, but I feel like they will have a better understanding if they work through it and figure it out for themselves.  As groups wrap up the last problem, I will call on reps from 6 different tables to work out the problems – showing their work and explaining their reasoning. 

Summarize + Homework

10 minutes