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← JEE Advanced 2015 · Paper 1
MathematicsMultiple correct+4 / -2Question 51 of 60

JEE Advanced 2015 · Paper 1, Mathematics question 51

In R3\mathbb R^3, consider the planes P1:y=0P_1:y=0 and P2:x+z=1P_2:x+z=1. Let P3P_3 be a plane, different from P1P_1 and P2P_2, which passes through the intersection of P1P_1 and P2P_2. If the distance of the point (0,1,0)(0,1,0) from P3P_3 is 1 and the distance of a point (α,β,γ)(\alpha,\beta,\gamma) from P3P_3 is 2, then which of the following relations is (are) true?

Choose one or more options
Answer and worked solution

Official answer: B, D

Planes through the line. P3P_3: x+z−1+λy=0x+z-1+\lambda y=0.

Distance from (0, 1, 0) equals 1.
∣λ−1∣2+λ2=1  ⟹  λ=−12.\frac{|\lambda-1|}{\sqrt{2+\lambda^2}}=1\implies\lambda=-\frac12.
So P3P_3 is 2x−y+2z−2=02x-y+2z-2=0.

Distance 2. ∣2α−β+2γ−2∣3=2\dfrac{|2\alpha-\beta+2\gamma-2|}3=2 gives
2α−β+2γ=8or−4.2\alpha-\beta+2\gamma=8\quad\text{or}\quad-4.

(B), (D)