Let α,β,γ,δ be real numbers such that α2+β2+γ2≠0 and α+γ=1 . Suppose the point (3,2,−1) is the  mirror image of the point (1,0,−1) with respect to the plane αx+βy+γz=δ . Then which of the  following statements is/are TRUE?

R is mid point of PQ∴R(2,1,−1) and it lies on plane  equation of plane is αx+βy+γz=δ∴2α+β−γ=δ …(1) Normal vector to plane is n→=2i+2jn→=2i+2j∴α2=β2=γ0=k∴α=2k,β=2k,γ=0 …...(2) and α+γ=1 (given).....(3)  from (2) and (3) ∴ α=1,β=1,γ=0 and from (1) 2(1)+1−0=δδ=3now:α+β=2δ−γ=3δ+β=4 so, A,B,C are correct.