Difficulty: Easy
Correct Answer: x^2 − 15x + 50 = 0
Explanation:
Introduction / Context:
Shifting roots by a constant k transforms the equation via the substitution y = x − k. If α, β are roots of f(y) = 0, then (α + k), (β + k) are roots of f(x − k) = 0. We use this to construct the new quadratic directly without solving for α and β numerically.
Given Data / Assumptions:
Concept / Approach:
Set y = x − 2 so that when x = α + 2, we have y = α (and similarly for β). Substitute y = x − 2 into the original polynomial and expand to get the desired equation in x.
Step-by-Step Solution:
Verification / Alternative check:
Sum of new roots = (α + β) + 4 = 11 + 4 = 15 ⇒ coefficient of x is −15 (matches). Product = (α + 2)(β + 2) = αβ + 2(α + β) + 4 = 24 + 22 + 4 = 50 (constant term matches).
Why Other Options Are Wrong:
Common Pitfalls:
Forgetting that shifting roots adjusts both sum and product: S′ = S + 2*2 and P′ = P + 2S + 4 for a shift of +2.
Final Answer:
x^2 − 15x + 50 = 0
Discussion & Comments