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The value of sum_(r=0)^(3) ""^(8)C_(r)(""^(5)C_(r+1)-""^(4)C_(r)) is "_____". |
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Answer» `= .^(8)C_(0) XX.^(4)C_(1)+.^(8)C_(1)xx.^(4)C_(2)+.^(8)C_(2)xx.^(4)C_(3)+.^(8)C_(3)xx.^(4)C_(4)` `=` coefficient of `x^(3)` in `(1+x)^(4)(1+x)^(8)` `=` coeficient of `x^(3)` in `(1+x)^(12)` `=.^(12)C_(3) = 220` |
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