Difficulty: Easy
Correct Answer: 0.86
Explanation:
Introduction / Context:
This expression is designed for the identity a^3 − b^3 = (a − b)(a^2 + ab + b^2). When the denominator matches a^2 + ab + b^2, the overall fraction collapses to a − b. Recognizing such structures converts a potentially tedious decimal computation into a one-step result.
Given Data / Assumptions:
Concept / Approach:
Apply the cube difference factorization. Since the denominator equals a^2 + ab + b^2 exactly, the expression simplifies to a − b immediately. Then compute 0.96 − 0.10 to reach the final answer without rounding issues.
Step-by-Step Solution:
Use identity: a^3 − b^3 = (a − b)(a^2 + ab + b^2).Given denominator = a^2 + ab + b^2, the ratio = a − b.Compute a − b = 0.96 − 0.10 = 0.86.
Verification / Alternative check:
Approximate directly: (0.884736 − 0.001) / (0.9216 + 0.096 + 0.01) ≈ 0.883736 / 1.0276 ≈ 0.86 (rounded), confirming the identity-based result.
Why Other Options Are Wrong:
Common Pitfalls:
Misreading 0.096 as 0.96; attempting to compute the cubes fully and rounding at intermediate steps; forgetting the identity and overcomplicating the work.
Final Answer:
0.86
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