np_(n)=np_(n-1)

11. Prove that nP_(r)=n(n-1)P_(r-1)

if nP_(r)=nP_(r+1) and nC_(r)=nC_(r-1) then value of (n+r) is equal to

If nC_(r)=nC_(r-1) and nP_(r)=nP_(r+1), then the value of n is

Let nP_(r) denote the number of permutations of n differenttaken r at a time.Then,prove that 1+1*1P_(1)+2*2P_(2)+3*3P_(3)+......+n*nP_(n)=n+1P_(n+)

Show that ^(^^)nP_(r)=(n-r+1)^(n)P_(r-1)

Prove that : "^nP_n= 2^nP_(n-2) .

Prove that nP_n=2 ^nP_(n-2)

Prove that nP_2= ^nP_(n-2)

Prove that P(n;r)=nP_(r)=n(!)/(n-r)!

If ^nP_r=^nP_(r+1) and ^nC_r=^nC_(r-1) then the values of n,r are