Advanced MathEasy–MediumCoefficient from a known root
Advanced Math practice question
The equation x² + bx + 12 = 0 has x = 3 as one of its solutions, where b is a constant. What is the value of b?
Answer: -7
9 + 3b + 12 = 0 gives 3b = −21, so b = −7.
Common wrong answers
- If you answered 7
- 7 has the sign wrong.
- If you answered -4
- −4 is the other root, not b.
- If you answered -21
- −21 is 3b.
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