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Find the numerically Greatest Term In the expansion of `(3-5x)^15` when x=1/5 |
Answer» We have `(3-5x)^(15)` For `|(T_(r+1))/(T_(r))|=(15-r+1)/(r) |-(5x)/(3)|ge 1` `rArr (16-r)/(r).(5xx1/5)/(3)ge1 ""("Putting" x = 1//5)` `rArr 16 - r ge 3r` `rArr le 4` Hence, `T_(4)` and `T_(5)` numerically the greatest terms, `T_(4) = .^(15)C_(3)3^(15-3)(-5x)^(3)` `= (-455 xx 3^(12) xx 5^(3))x^(3)` and `T_(5) = .^(15)C_(4)3^(15-4)(-5x)^(4)` `= (455 xx 3^(12) xx 5^(3))x^(4)` Also , for numerical value, `|T_(4)| = |T_(5)| = 455 xx 3^(12) 5^(3)` |
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