Algebraic proof: justifying each step
- Every line legal, and the last line false — 3 tasks
- How one line hands you the next — 3 tasks
- A reason for every line — 3 tasks
- The same reasons, now on a figure — 3 tasks
- Reading what a property asserts — 3 tasks
- Practice — 27 tasks
- Summary — 2 tasks
- Cool-down — 3 tasks
Classroom activities
Things a class does rather than writes on. Each one is a finished PDF: print it, cut it up if it says so, and hand it round.
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Algebraic Proof: Both Sides, One Side, or Not Allowed? — Cut & Glue Sort 25 minutes · 5 sheets
Twelve steps of algebra to cut out and sort: does the step do the same thing to both sides, change only how one side is written, or not follow at all?
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Algebraic Proof: Which Reason Fits? — Maze 10–15 minutes · 4 sheets
Eight boxes, each one step of an algebraic chain with two reasons to choose from. The right reason leads on; the look-alike leads to a box that sends the student back.
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Algebraic Proof: Is That the Right Reason? — Mystery Picture 25–35 minutes · 4 sheets
Twenty-five steps of algebraic chains, each with a reason printed under it. Every step is correct; only the name can be wrong. Right name, fill the square — and a picture appears.
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Algebraic Proof: A Reason for Every Line — Scavenger Hunt a full class period · 13 sheets
16 cards around the room, each a finished chain of equations with the reasons missing: find the line that uses the reason named on the card, read its number, and find that number at the top of another card. A wrong answer lands on a card that sends the group back; a clean run is 8 lines.