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Find the term independent of `x` in the expansion of `(3x - (2)/(x^(2)))^(15)`. |
Answer» Given expansion is `(3x - (2)/(x^(2)))^(15)` Let `T_(r + 1)` is the general term. `:. T_(r + 1) = .^(15)C_(r) (3x)^(15 - r) ((-2)/(x^(2)))^(r) = .^(15)C_(r) (3x)^(15 - r) (- 2)^(r) x^(-2r)` `= .^(15)C_(r) 3^(15 - r) x^(15 - 3r) (-2)^(r)` For independent of x, `15 - 3r = 0 rArr r = 5` Since, `T_(5 + 1) = T_(6)` is independent of x. `T_(5 + 1) = .^(15)C_(r) 3^(15 - 5) (-2)^(5)` `= - (15 xx 14 xx 13 xx 12 xx 11 xx 10 !)/(5 xx 4 xx 3 xx 2 xx 1 xx 10 !) . 3^(10).2^(5)` `= -3003.3^(10). 2^(5)` |
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