1.(multiple answer possible) If the sum of the coefficients in the expansion of (2x+y-z)^n is 128, then the value of r for which the coefficient of x^r in the expansion of (1+x)^n is the greatest is
(A) 7 (B)3 (C)4 (D)5
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1 Answers
Manish Shankar
·2014-03-24 23:50:24
putting x=y=z=1 in first equation,
2n=128
so n=7
Now in (1+x)7, greatest terms are the middle terms
- Pratyasha Das thank u..there is no other way to solve apart from assuming x=y=z=1?
Upvote·0· Reply ·2014-03-26 00:18:24
- Anindita Roy How can we make such assumptions ?