Advanced Math practice question

Answer: 23

Square both sides: (x + 1/x)² = x² + 2 + 1/x² = 25. So x² + 1/x² = 25 − 2 = 23.

Common wrong answers

If you answered 10

10 is 5 × 2, doubling instead of squaring.

If you answered 25

25 is (x + 1/x)², which includes the cross term 2·x·(1/x) = 2.

If you answered 27

27 adds the 2 instead of subtracting it.

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