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The coefficient of `x^(20)` in ` (1 + 3x + 3x^(2) + x^(3))^(20)`,I sA. `""^(60)C_(40)`B. `""^(30)C_(20)`C. `""^(15)C_(2)`D. none of these |
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Answer» Correct Answer - a We have , `(1 + 3x + 3x^(2) + x^(3))^(20) = { (1+ x)^(3) }^(20) = (1 + x)^(60)` `therefore ` Coefficient of `x^(20) ` in` (1 + 3x + 3x^(2) + x^(3))^(20)` = Coefficient of `x^(20)` in `(1 + x)^(60) = ""^(60)C_(20) = ""^(60)C_(40)` |
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