If (1+x)n=C0+C1x+C2x2+.......+Cnxn, then C1C0+2C2C1+3C3C2+........+nCnCn−1=
n(n−1)2
n(n+2)2
n(n+1)2
(n−1)(n−2)2
C1C0+2⋅C2C1+3⋅C3C2+........+n⋅CnCn−1
=n1+2n(n−1)1.2n+3n(n−1)(n−2)3.2.1n(n−1)1.2+......+n.1n
=n+(n−1)+(n−2)........+1=∑n=n(n+1)2
If (1+x)n=C0+C1x+C2x2+.......+Cnxn, then
C1C0 + 2C2C1 + 3C3C2 + ........+ nCnCn−1 =