Difficulty: Medium
Correct Answer: 9
Explanation:
Introduction / Context:
Algebraic manipulations often simplify dramatically when a + b + c = 0. This question checks whether you can exploit that condition to reduce complicated rational expressions. Recognizing that sums like a + b equal −c is the main lever to collapse each fraction to simple constants.
Given Data / Assumptions:
Concept / Approach:
Use the identity implied by the condition: a + b = −c, b + c = −a, c + a = −b. Substituting these into all numerators and denominators instantly converts each fraction into −1, which makes each bracket sum straightforward. Finally, multiply the two summed values.
Step-by-Step Solution:
Since a + b = −c, (a + b)/c = (−c)/c = −1.Similarly, (b + c)/a = (−a)/a = −1, and (c + a)/b = (−b)/b = −1.Therefore the first bracket equals (−1) + (−1) + (−1) = −3.In the second bracket: a/(b + c) = a/(−a) = −1; b/(c + a) = b/(−b) = −1; c/(a + b) = c/(−c) = −1.So the second bracket also equals −3.Product = (−3) * (−3) = 9.
Verification / Alternative check:
Pick a concrete triple with sum zero, e.g., a = 1, b = 2, c = −3. Substitute to verify each fraction is −1. The product again equals 9.
Why Other Options Are Wrong:
Common Pitfalls:
Attempting to find a common denominator instead of exploiting a + b + c = 0; sign errors when converting a + b to −c.
Final Answer:
9
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