Difficulty: Medium
Correct Answer: 9
Explanation:
Introduction / Context:
This algebra question probes symmetry and substitution when a + b + c = 0. Recognizing how this constraint transforms compound fractions allows a short, elegant evaluation without heavy computation.
Given Data / Assumptions:
Concept / Approach:
From a + b + c = 0, we have a + b = −c, b + c = −a, and c + a = −b. Substitute these into each fraction to simplify immediately.
Step-by-Step Solution:
S1 termwise: (a + b)/c = (−c)/c = −1; (b + c)/a = (−a)/a = −1; (c + a)/b = (−b)/b = −1.Hence S1 = (−1) + (−1) + (−1) = −3.S2 termwise: a/(b + c) = a/(−a) = −1; b/(c + a) = b/(−b) = −1; c/(a + b) = c/(−c) = −1.Hence S2 = (−1) + (−1) + (−1) = −3.Product: S1 × S2 = (−3) * (−3) = 9.
Verification / Alternative check:
Pick a simple triple satisfying a + b + c = 0, e.g., a = 1, b = 2, c = −3, and evaluate numerically to confirm S1 = S2 = −3.
Why Other Options Are Wrong:
0, 8, −3, and 3 ignore the paired substitutions that force each sum to −3; only the product 9 matches.
Common Pitfalls:
Forgetting that b + c = −a, etc.; attempting to find a common denominator instead of using the given linear constraint for direct simplification.
Final Answer:
9
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