The coefficient of `1//x` in the expansion of `(1+x)^n(1+1//x)^n` is `(n !)/((n-1)!(n+1)!)` b. `((2n)!)/((n-1)!(n+1)!)` c. `((2n)!)/((2n-1)!(2n+1)!)` d. none of these

Options

A. `(n!)/((n-1)!(n+1)!)`
B. `(2(n)!)/((n-1)!(n+1)!)`
C. `(2(n)!)/((2n-1)!(2n+1)!)`
D. None of these

Answer

B