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Here is a line from an old page: 5a² + 10a. No question. No answer. What can you do with it?

Your book's chapter is Algebra Play, Part II, Chapter 6. It uses letters to explain number tricks, number pyramids and calendar squares. A number pyramid stacks numbers in rows. This track builds the moves those explanations need.

What you will learn

• Parts — a term is one piece of a sum. Split it into number and letters.
• Joining — same letters join. Only the number changes.
• Term times term — multiply the numbers, write the letters side by side.
• Into a bracket — one term reaches every term inside.
• Two brackets — every term meets every term.
• A square in four pieces — a sum times itself, as a picture.
• The easy way round — a shortcut for 98 × 98.
• Taking a factor out — undo the opening of a bracket.
• Putting a number in — shows when a rewritten line is wrong.
• A trick, as a line — "Think of a number", explained.

Every idea has one small lab. Tap or slide, and see the line stay true.