Advanced MathMediumx² coefficient in a binomial-trinomial product
Advanced Math practice question
When (x + 3)(x² − 2x + 4) is expanded, what is the coefficient of x²?
Answer: 1
x² terms come from x · (−2x) and 3 · x²: −2x² + 3x² = x², so the coefficient is 1.
Common wrong answers
- If you answered 3
- 3x² from 3 · x² must be combined with −2x² from x · (−2x).
- If you answered 5
- The two contributions have opposite signs: 3 − 2 = 1.
- If you answered -2
- −2x² from x · (−2x) must be combined with +3x² from 3 · x².
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What are the solutions to x² + 6x + 8 = 0?
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