Let α ,   β ,   γ ,   δ be real numbers such that α 2 + β 2 +…

Let α, β, γ, δ be real numbers such that α2+β2+γ20 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?
  1. α+β=2
  2. δ-γ=3
  3. δ+β=4
  4. α+β+γ=δ

Solution

From the diagram,

Mid point of A & A' lies on the plane, i.e.,  B2,1,-1

2α+β-γ=δ1

α+γ=1  .2

Direction Ratio of AA'2,2,0 will be proportional to normal to the plane,

α2=β2=γ0=λ

α=2λ, β=2λ, γ=0

2λ+0=1 λ=12

α=1, β=1, γ=0, δ=3

Now,

(A) α+β+γ=1+1+0=2δ

(B) α+β=1+1=2
(C) δ+β=3+1=4
(D) δ-γ=3

Asked in: JEE Advanced 2020 (Paper 2)

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