Which of the following is the correct expansion of (x - y)³?

Practice Questions

Q1
Which of the following is the correct expansion of (x - y)³?
  1. x³ - 3x²y + 3xy² - y³
  2. x³ - y³
  3. x³ - 3xy² + 3x²y - y³
  4. 3x²y - 3xy²

Questions & Step-by-Step Solutions

Which of the following is the correct expansion of (x - y)³?
  • Step 1: Understand that (x - y)³ means (x - y) multiplied by itself three times: (x - y) * (x - y) * (x - y).
  • Step 2: First, calculate (x - y) * (x - y). This gives you x² - 2xy + y².
  • Step 3: Now, take the result from Step 2, which is (x² - 2xy + y²), and multiply it by (x - y) again.
  • Step 4: Distribute (x - y) across (x² - 2xy + y²): First, multiply x by each term: x * x² = x³, x * (-2xy) = -2x²y, and x * y² = xy².
  • Step 5: Now, multiply -y by each term: -y * x² = -yx², -y * (-2xy) = 2y²x, and -y * y² = -y³.
  • Step 6: Combine all the results from Steps 4 and 5: x³ - 2x²y + xy² - yx² + 2y²x - y³.
  • Step 7: Rearrange and combine like terms: x³ - 3x²y + 3xy² - y³.
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