If Cr=nCr and (C0+C1)(C1+C2)...(Cn−1+Cn)=k (C0C1C2...Cn) then the value of k equals
nCr+1+nCr
=n+1Cr+1
Hence simplifying the terms, we get
n+1C1.n+1C2....n+1Cn
Now
n+1C1
=(n+1)!n!.1!
=(n+1)nnC1
Similarly
n+1C2
=(n+1)!(n−1)!.2!
=(n+1)(n−1)nC2
Hence substituting, in the above expression, we get
(n+1)nn!(nC0.nC1...nCn)
Comparing coefficients, we get
K=(n+1)nn!