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MathNet 2026 — Part 02 Question 156

Math Olympiad Vault · MathNet 2026 — Part 02

Question 156

squares difference - if $(x+y)^2-(x-y)^2=20$, then $x y$ is equal to:
  1. 0
  2. 1
  3. 2
  4. 5
  5. 10