Advanced MathVery hardQuotient of a cubic by a known linear factor
Advanced Math practice question
The polynomial p(x) = x³ − 4x² + x + 6 has (x − 2) as a factor. Which expression is the quotient when p(x) is divided by (x − 2)?
- A. x² − 2x − 3Correct
- B. x² + 2x − 3
- C. x² − 2x + 3
- D. x² − 6x + 13
Answer: A. x² − 2x − 3
Divide, or match coefficients: (x − 2)(x² + bx + c) = x³ + (b − 2)x² + (c − 2b)x − 2c. So b − 2 = −4 gives b = −2, and −2c = 6 gives c = −3; check c − 2b = −3 + 4 = 1. ✓ The quotient is x² − 2x − 3.
Why the other answers are wrong
- B. x² + 2x − 3
- (x − 2)(x² + 2x − 3) = x³ − 7x + 6, wrong x² and x terms.
- C. x² − 2x + 3
- (x − 2)(x² − 2x + 3) has constant −6, not +6.
- D. x² − 6x + 13
- (x − 2)(x² − 6x + 13) = x³ − 8x² + 25x − 26.
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