Algebraic identity application: Evaluate (2.247)^3 + (1.730)^3 + (1.023)^3 - 3 * 2.247 * 1.730 * 1.023, divided by [(2.247)^2 + (1.730)^2 + (1.023)^2 - 2.247*1.730 - 1.730*1.023 - 2.247*1.023].

Difficulty: Easy

Correct Answer: 5

Explanation:


Introduction / Context:
This problem directly uses a well-known algebraic identity. When x + y + z ≠ 0, the expression (x^3 + y^3 + z^3 - 3xyz) / (x^2 + y^2 + z^2 - xy - yz - zx) simplifies elegantly to x + y + z.


Given Data / Assumptions:

  • x = 2.247, y = 1.730, z = 1.023
  • We assume standard algebraic identities apply and no rounding is needed before substitution.


Concept / Approach:
Use the identity: (x^3 + y^3 + z^3 - 3xyz) / (x^2 + y^2 + z^2 - xy - yz - zx) = x + y + z, provided x + y + z ≠ 0. Here, the numbers are chosen so their sum is exact and simple.


Step-by-Step Solution:

Compute sum: x + y + z = 2.247 + 1.730 + 1.023 = 5.000By identity, the entire fraction simplifies to x + y + z = 5


Verification / Alternative check:

You can numerically evaluate numerator and denominator separately, but the identity guarantees the result as long as x + y + z ≠ 0.


Why Other Options Are Wrong:

  • 1.730, 4, 5.247: These are distractors derived from partial sums or misapplied identities. Only the exact sum 5 satisfies the identity here.


Common Pitfalls:

  • Attempting to expand everything numerically, increasing chances of arithmetic error.
  • Forgetting the identity or misremembering coefficients.


Final Answer:

5

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