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The value of the term independent of x in the expansion of `(x^(2)-(1)/(x))^(9)` is :A. 9B. 18C. 48D. 84 |
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Answer» Correct Answer - D `(x^(2)-(1)/(x))^(9)` `t_(r+1)=.^(9)C_(r)(x^(2))^(9-r)((-1)/(x))^(r)` `.^(9)C_(r)x^(18-2r).(-1)^(r).x^(-r)` `=.^(9)C_(r)(x)^(18-3r)(-1)^(r)" "...(1)` Term will be independent of x when 18 - 3r = 0 r = 6 Put r = 6, in [1] `t_(7)=.^(9)C_(6)(-1)^(6)=(9!)/(6!3!)=84` |
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