Questions
If sum of the coefficients in the expansion of is 128., then coefficient of x in the expansion of is
a
51
b
48
c
35
d
28
detailed solution
Correct option is C
Sum of the coefficients in the expansion of x+1xnis equal to 2n .∴ 2n=128=27⇒n=7Now, Tr + 1, the (r + 1)th term in the expansion of x+1x7is Tr+1=7Crx7−r1xr=7Crx7−2rFor the coefficient of x, we set 7 – 2r = 1⇒ r = 3.Thus, coefficient of x in the expansion of x+1x7is 7C3=35Talk to our academic expert!
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The sum of the real values of x for which the middle term in the binomial expansion of equals 5670 is
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