Advanced Math practice question

Answer: 29

(x − y)² = x² − 2xy + y², so x² + y² = (x − y)² + 2xy = 9 + 20 = 29.

Common wrong answers

If you answered 19

19 adds xy once instead of twice.

If you answered 49

49 is (x + y)², which is 9 + 4(10).

If you answered -11

−11 subtracts 2xy instead of adding.

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