Two numbers have sum 8 and difference 4. Form the quadratic equation having these numbers as roots, and pick the correct option.

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:

  • Sum S = 8.
  • Difference D = 4 (so numbers are (S ± D)/2).
  • Quadratic desired with those numbers as roots.


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

Discussion & Comments

No comments yet. Be the first to comment!
Join Discussion