Difficulty: Easy
Correct Answer: x^2 - 8x + 12 = 0
Explanation:
Introduction / Context: From the sum and difference of two numbers, you can determine the numbers and then the quadratic having them as roots. This illustrates reverse construction of a polynomial from root properties.
Given Data / Assumptions:
Concept / Approach: Compute the two numbers, then use x^2 − Sx + P = 0, where P is their product. Alternatively, directly use S and P without computing the numbers individually.
Step-by-Step Solution:
Numbers: (8 ± 4)/2 ⇒ 6 and 2.Sum S = 8, Product P = 6 * 2 = 12.Quadratic: x^2 − Sx + P = x^2 − 8x + 12 = 0.Verification / Alternative check: Factor: (x − 6)(x − 2) = x^2 − 8x + 12 ⇒ roots 6 and 2, consistent.
Why Other Options Are Wrong: Sign errors in the x-term or constant term change the sum/product, creating different roots.
Common Pitfalls: Taking D itself as a root or misusing S and P in the formula.
Final Answer: x^2 − 8x + 12 = 0
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