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We Distribute, Yet Things Multiply

Joining only the pieces of one kind

Expanding (x + 2)(x + 3) leaves four terms: x², 3x, 2x and 6. Which of them can gather into one term?

Four terms from an expansion.
Step 1 of 4
  1. Four terms from an expansion.
  2. x² goes to the square pile.
  3. 3x and 2x join: 5x.
  4. 6 goes to the number pile. Answer: x² + 5x + 6.

Joining only the pieces of one kind

Only 3x and 2x can gather, into 5x.

Like terms — terms with exactly the same letter part. The letter part of 5x² is x².

Rule: two terms gather only when their letter parts match exactly. x² and 5x do not match. The letter is used twice in x² but once in x.

  • 3x + 2x = 5x
  • x² and 5x stay apart
  • 3xy and 2x stay apart too

3x is 3 times x, and 2x is 2 times x. So together they make 5 times x.

Sort the four terms. Tap a term to move it, or drag it.

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This track

  1. 0 Start here
  2. 1 The cut that moves nothing
  3. 2 The number outside meets every term inside
  4. 3 The same move with a letter inside
  5. 4 A minus that reaches every term
  6. 5 Two brackets, and every pairing between them
  7. 6 Joining only the pieces of one kind
  8. 7 The middle piece that goes missing
  9. 8 Splitting a number on purpose
  10. 9 The big picture
  11. 10 Track quiz

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