Difficulty: Hard
Correct Answer: 1/4
Explanation:
Introduction / Context:
This is a nonstandard but elegant manipulation with roots of a quadratic. Define A = (α^2/β)^{1/3} and B = (β^2/α)^{1/3}. We are to find S = A + B. Using identities for A^3 + B^3 and AB, we can form a cubic in S and then locate the rational value among the options that satisfies it.
Given Data / Assumptions:
Concept / Approach:
We use (A + B)^3 = A^3 + B^3 + 3AB(A + B). Compute A^3 + B^3 in terms of α, β using the identity α^3 + β^3 = (α + β)^3 − 3αβ(α + β), then divide by αβ. Compute AB directly as (αβ)^{1/3}. Substitute into the cubic for S and solve by testing the given rational choices.
Step-by-Step Solution:
Verification / Alternative check:
None of the other options satisfy the cubic. Since the cubic has S = 1/4 as a root and other options are far off, 1/4 is the correct value.
Why Other Options Are Wrong:
Common Pitfalls:
Arithmetic slips when converting to a common denominator or when dividing by P. Keep fractions exact; avoid decimals to prevent rounding errors.
Final Answer:
1/4
Discussion & Comments