Advanced MathHardConstant that removes the linear term of a product
Advanced Math practice question
When (3x + a)(x − 2) is expanded, the result has no x term, where a is a constant. What is the value of a?
Answer: 6
(3x + a)(x − 2) = 3x² − 6x + ax − 2a = 3x² + (a − 6)x − 2a. For no x term, a − 6 = 0, so a = 6.
Common wrong answers
- If you answered 2
- 2 is the constant in (x − 2), not a.
- If you answered 3
- 3 is the coefficient of x in the first factor.
- If you answered -6
- −6 gives an x coefficient of −12, not 0.
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