Find the ratio of the coefficients of xn and xq in the expansion of (1+x)p+q.
Coefficients of xn in the expansion of (1+x)2nis2nCn=a
Coefficients of xn in the expansion of (1+x)2n−1is2n−1Cn=b
Now,
ab=2nCn2n−1Cn=(2n)!n!n!(2n−1)!n!(n−1)!=2nn=2
Hence, ab=2.