# Algebraic Expressions Lesson 1 Episode 4 (Teachers)

### Reflecting

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Stop the video above first if it is playing.

The students work to explain what each symbol in their equation means in the pool context and encounter a challenge.

### Episode Supports

Students’ Conceptual Challenges

1. Haleemah’s initial attempts to show where x is in the diagram of the pool are imprecise and indicate she might not be sure what x means. At 1:52 she says “x is all of this, everything around.” At 4:00 she says that every side would be x, as she circles each side of the pool. This is a common challenge for students—identifying with specificity the quantity for which a variable is being used.
2. When asked where the x – 2 is, Haleemah correctly describes a process of finding x (the number of tiles in one of the sides) and then removing the two corners. Another important interpretation of x – 2 is as the number of tiles left (after taking away the two corner tiles). Haleemah struggles to see x – 2 as the number of tiles between two corners [6:49]. She resolves this challenge later in Episode 5.

Focus Questions

For use in a classroom, pause the video and ask these questions:

1. [Pause the video at 4:54] What do you think Haleemah means when she says that every side would be x? Do you agree or disagree with her? How would you describe what x is?
2. [Pause the video at 6:50] What would you say to Haleemah to help her understand where x – 2 is in the diagram? Turn and discuss with a partner.

Supporting Dialogue

Ask students to examine their own equations and expressions from before. Have them take turns explaining the meaning of any values or letters they used in their equations. For each letter or value ask, “What does this mean in the pool context? Where do you see it in the pool diagram?”