Difficulty: Easy
Correct Answer: 0
Explanation:
Introduction / Context:
This is a direct application of the identity p^3 + q^3 + r^3 − 3pqr = (p + q + r)(p^2 + q^2 + r^2 − pq − qr − rp). Whenever p + q + r = 0, the entire expression simplifies to 0. The shifts by 4, 3, and 1 are designed precisely to make the sum vanish.
Given Data / Assumptions:
Concept / Approach:
Compute p + q + r and use the cubes identity. If p + q + r = 0, then p^3 + q^3 + r^3 − 3pqr must be 0, regardless of the actual individual values of a, b, and c.
Step-by-Step Solution:
Verification / Alternative check:
Plug in any specific numbers satisfying a + b + c = 8, e.g., a = 4, b = 3, c = 1. Then each bracket becomes 0, making the expression 0 immediately.
Why Other Options Are Wrong:
Any nonzero value would contradict the identity when p + q + r = 0.
Common Pitfalls:
Forgetting the shift and computing cubes of a, b, c directly; or using incorrect variations of the identity.
Final Answer:
0
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