GIVEN term can be WRITTEN as \[{{(1+X)}^{2}}{{(1-x)}^{-2}}\] \[=(1+2x+{{x}^{2}})[1+2x+3{{x}^{2}}+....+(n-1){{x}^{n-2}}\] \[={{x}^{n}}(n+1+2n+n-1)+....\] THEREFORE coefficient of \[{{x}^{n}}\] is 4n.