If Cr=nCr and (C0+C1)(C1+C2)....(Cn−1+Cn)=k(n+1)nn! , then the value of k is :
(C0+C1)(C1+C2)(C2+C3)....(Cn−1+Cn)
= C1C2...Cn(1+C0C1)(1+C1C2)....(1+Cn−1Cn)
= C1C2....Cn(n+1n)(n+1n).....(1+n1)
= C1C2.....Cn.(n+1)nn!
= C0C1C2....Cn.(n+1)nn! [ C0=1]
∴ k = C0C1C2......Cn.