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The value of `(30 0)(30 10)-(30 1)(30 11)+(30 2)(30 12)++(30 20)(30 30)=``^60 C 20`b. `^30 C 10`c. `^60 C 30`d. `^40 C 30`A. `""^(30)C_(11)`B. `""^(60)C_(10)`C. `""^(30)C_(10)`D. `""^(65)C_(55)` |
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Answer» Correct Answer - c We have, `""^(30)C_(0)xx""^(30)C_(10)- ""^(30)C_(1)xx""^(30)C_(11)+...+ ""^(30)C_(10)xx""^(30)C_(0)` = Coefficient of `x^(20)` in `{(1 + x )^(30) (1 - x)^(30)}` = Coefficient of `x^(20)` in ` (1 - x^(2))^(30)` ` = ""^(30)C_(10) (-1)^(10) = ""^(30)C_(10)` |
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