Difficulty: Medium
Correct Answer: 1000001
Explanation:
Introduction / Context:
This question tests algebraic expansion and recognition of a well-known binomial pattern. The expression a(a^2 − 3a + 3) can be rewritten in terms of (a − 1)^3, making evaluation for a = 101 very fast.
Given Data / Assumptions:
Concept / Approach:
First expand:
a(a^2 − 3a + 3) = a^3 − 3a^2 + 3a.
Now recall:
(a − 1)^3 = a^3 − 3a^2 + 3a − 1.
So:
a^3 − 3a^2 + 3a = (a − 1)^3 + 1.
Then substitute a = 101 to compute (100^3 + 1).
Step-by-Step Solution:
1) Expand the product:
a(a^2 − 3a + 3) = a^3 − 3a^2 + 3a
2) Compare with (a − 1)^3:
(a − 1)^3 = a^3 − 3a^2 + 3a − 1
3) Therefore:
a^3 − 3a^2 + 3a = (a − 1)^3 + 1
4) Substitute a = 101:
(a − 1)^3 + 1 = 100^3 + 1
5) Compute 100^3:
100^3 = 100 * 100 * 100 = 1,000,000
6) Add 1:
1,000,000 + 1 = 1,000,001
Verification / Alternative check:
Direct computation also works:
101^3 = 1,030,301; 3a^2 = 3*10,201 = 30,603; 3a = 303.
Then 1,030,301 − 30,603 + 303 = 1,000,001. Same result.
Why Other Options Are Wrong:
• 1,000,000: misses the +1 from the (a − 1)^3 relationship.
• 999,999: incorrect subtraction handling.
• 1,010,101 and 1,030,301: common distractors from partial computations like a^3 alone.
Common Pitfalls:
• Expanding incorrectly (especially the −3a term).
• Not recognizing the (a − 1)^3 + 1 pattern that makes it fast.
Final Answer:
1000001
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