If `.^nP_r=504`,`.^nC_r=84`find n and r.

if ^nP_r= ^nP_(r+1) and ^nC_r= ^nC_(r-1) find n and r.

If ^nP_r=^nC_r x ,then x=?

if ^nC_12= ^nC_8 find n.

A boy instead of writing .^nP_r writes .^nC_r By what number should he multiply his result to get the correct answer?

Find Z-(R-Z) .

Find the values of n and r if ""^nP_r=336,""^nC_r=56 .

Prove that .^(n-1)P_r+r.^(n-1)P_(r-1)=^nP_r .

InFig.8.13,find tanP-cot R

Show that ^nC_r+2. ^nC_(r-1)+ ^nC_(r-2)= ^(n+2)C_r

Prove one of the following: ^nC_r+^nC_(r-1)=^(n+1)C_r .