Advanced MathHardFactoring by grouping
Advanced Math practice question
The expression x²(x − 1) − 4(x − 1) factors completely as (x − 1)(x + a)(x − a), where a is a positive constant. What is the value of a?
Answer: 2
Factor out (x − 1): (x − 1)(x² − 4) = (x − 1)(x + 2)(x − 2). So a = 2.
Common wrong answers
- If you answered 1
- 1 is the constant in the common factor (x − 1).
- If you answered 4
- 4 is the constant in x² − 4, before taking its square root.
- If you answered -2
- −2 is ruled out because a is positive.
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