It’s time to teach algebraic expressions. Your students need to know how to add and subtract monomials. Easy, right?
You launch into your lesson and start to hear questions like this:
- “4x? What am I supposed to do with that?”
- “3x + 2y has to equal 5xy.”
- “Is this dot between the 5 and the x a decimal point?”
- “x^2 is the same as x times 2.”
This is a sign that you need to take a step back and make sure your students really understand algebraic expressions before you jump on in.
1. Dissect an expression
Give your students an expression and have them label all of the parts. This will help you to see what they know and what they might need to know.
2. Talk about the four ways to show multiplication
Start off by showing a multiplication sentence like this:
4 x n
Then show 4 dot n.
What do they notice? What do they wonder?
Now show 4(n).
What do they notice? What do they wonder?
Finally, show 4n.
What do they notice? What do they wonder?
3. Model algebraic expressions with algebra tiles
Algebra tiles are great tools to add and subtract monomials. Students will be able to see how terms are combined and removed.
4. Model algebraic expressions with number lines
Number lines can be helpful when you want students to see what’s left when you remove something and when you want them to see how much more something is than something else
5. Evaluate expressions by thin slicing
Create a sequence of problems where only one thing is changed each time.
Evaluate when n=5
4 x n
4n
4n + 1
4n – 1
Evaluate when n=5 and m=1.4
n + m
4n + m
4n – m
4n + m + 3n
4n + m + 3n + 2m
6. Make a connection between algebraic expressions and formulas
Give students a question that requires them to substitute variables into a formula, like the area of a triangle or parallelogram. You will start to see the light bulbs going off. “Oh…this is why we do this!”
If you found this helpful, make sure to check out this Algebraic Expressions Math Workshop. With guided math task cards, a tic-tac-toe game, a Google Sheets mystery picture and a practice worksheet your students will walk away with a deep understanding of representing and evaluating algebraic expressions.
Not quite sure what Math Workshop is all about? Click here to learn more.
I’m Lauren, from “From Math to Music” – your go-to person for all things Math and Classroom Community.
Being a middle-school teacher and a mom of 3, I know how hard it is for busy teachers to create resources that allow for deep thinking and build classroom community. That's why I love sharing tips and tricks that you can you use in your middle school classroom right this minute.
