Equivalent expressions

Target: Decide whether two expressions always name the same value.

Language target: Use “for every value of x.”

Likely miss: Students choose an expression that matches only the first term.

Ask: What happens when you test x = 1?

If you see it: Have them test both expressions at x = 1 and x = 2.

Evidence to listen for: A counterexample eliminates a false match.

Next: Testing values is the next step if symbolic rewriting is fragile.

Observable student moves: names both quantities, uses the represented relationship, and revises after feedback. This companion is not a score.