(1+x)n=nC0×1(n−0)×x0+nC1×1(n−1)×x1+nC2×1(n−2)×x2+....+nCn×1(n−n)×xn Calculation: Given expansion is (1+x)2n =2nC0×1(2n−0)×x0+2nC1×1(2n−1)×x1+...+2nC2n×1(2n−2n)×x2n First term =2nC0×1×1=1 Last term =2nC2n×1×x2n=1×x2n=x2n ∴ Sum =1+x2n Coefficient of 1=1, coefficient of x2n=1 So, sum of the coefficients =1+1=2