Question
In the expansion of (1+x1−x)2, the coefficient of xn
Answer: Option A
:
A
Given term can be written as (1+x)2(1−x)−2
=(1+2x+x2)[1+2x+3x2+.......+(n−1)xn−2+nxn−1+(n+1)xn+...........]
= xn(n+1+2n+n−1)+..........
Therefore coefficient of xn is 4n.
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:
A
Given term can be written as (1+x)2(1−x)−2
=(1+2x+x2)[1+2x+3x2+.......+(n−1)xn−2+nxn−1+(n+1)xn+...........]
= xn(n+1+2n+n−1)+..........
Therefore coefficient of xn is 4n.
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