If n and r are positive integers such that`0ltrltn` then show that the roots of the quadratic equation`nC_r x^2+2. ^nC_(r+1)x+^nC_(r+2)=0` are real.

If n and r are positive integers such that 0ltrltn then roots of the equation ^nC_r x^2+2.^nC_(r+1)x+^nC_(r+2)=0 are necessarily (A) imaginary (B) real and equal (C) real and unequal (D) real but may be equal or unequal

nC_r+2. nC_(r-1)+nC_(r-2)=

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

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

Prove that nC_r = nC_(n-r)

If 2lerlen show that ^nC_r +2 ^nC_(r-1) +^nC_(r-2)=^(n+2)C_r

Prove that ^"" nC_r=^nC_(n-r)