Advanced Math practice question

Answer: 35

x² − 2x − 15 = 0 → (x − 5)(x + 3) = 0 → x = 5. Then x² + 2x = 25 + 10 = 35.

Common wrong answers

If you answered 3

3 comes from x = −3, which is not positive.

If you answered 5

5 is x, not x² + 2x.

If you answered 15

15 is the given value of x² − 2x.

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