Advanced Math practice question

Answer: 65/8 or 8.125

x + 1/x = 5/2 gives 2x² − 5x + 2 = 0, so x = 2 (since x > 1); then x³ + 1/x³ = 8 + 1/8 = 65/8.

Common wrong answers

If you answered 2

2 is x alone.

If you answered 8

8 is x³ alone.

If you answered 125/8

125/8 cubes 5/2 without subtracting the cross terms.

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