16Hit1600
Advanced MathVery hardConstant in a sum of cubes

Advanced Math practice question

For all values of x, (x + 2)(x² − 2x + 4) = x³ + k, where k is a constant. What is the value of k?

Answer: 8

The x² and x terms cancel, leaving x³ + 2 × 4 = x³ + 8.

Common wrong answers

If you answered 2
2 is the constant in the first factor.
If you answered 4
4 is the constant in the second factor.
If you answered -8
−8 has the wrong sign; the constant is +2 × +4.

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