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If the number of terms in the expansion of `(1-2/x+4/(x^2))^n , x!=0,`is 28, then the sum of the coefficients ofall the terms in this expansion, is :(1) 64(2) 2187(3) 243(4) 729A. 2187B. 243C. 729D. 64 |
Answer» Correct Answer - C Theroectically the number of terms are `2n+1`(i.e, odd) But given that number of term is `28`. So considering number of term `= .^(n+2)C_(2) = 28`. (Here we are ignoring clubbing of terms) `:. N = 6` `:.` Sum of coefficient `= 3^(n) = 3^(6) = 729` (Putting `x = 1`) |
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