Advanced MathHardFactoring out a common binomial
Advanced Math practice question
The expression (2x + 1)(x − 3) − (x − 3)² can be written as (x − 3)(x + k), where k is a constant. What is the value of k?
Answer: 4
Factor out (x − 3): (x − 3)[(2x + 1) − (x − 3)] = (x − 3)(x + 4). So k = 4.
Common wrong answers
- If you answered 1
- 1 keeps only the constant of the first factor.
- If you answered -2
- −2 comes from (2x + 1) − (x + 3), not distributing the minus sign to −3.
- If you answered -4
- −4 has the wrong sign.
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