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Find the coefficient of x¹¹ in the expansion of (1 + x²)⁴ * (1 + x³)⁷ * (1 + x⁴)¹².
- 1051
- 1106
- 1113
- 1120
Correct answer: 1113
Solution
By systematically listing all (a,b,c) with 2a+3b+4c=11 and computing C(4,a)*C(7,b)*C(12,c) for each, the total sums to 1113.
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