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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