Advanced Math practice question

Answer: 9

(2x + k)² = 4x² + 4kx + k², so 4k = 12, k = 3 and c = 9.

Common wrong answers

If you answered 3

3 is k, not c.

If you answered 36

36 squares the 6 from halving 12 twice, a slip.

If you answered 144

144 squares 12.

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