JEE Previous Year Question

For real numbers α and β ≠ 0, if the point of intersection of the straight lines and ,lies on the plane x + 2y − z = 8, then α − β is equal to :

Topic: JEE PYQ

Answer: D. Full step-by-step solution below.

  1. A5
  2. B9
  3. C3
  4. D7

Correct answer: D

Solution

(d)
First line is (ϕ + α, 2ϕ + 1, 3ϕ + 1) and second line is f (qβ + 4, 3q + 6, 3q + 7) For ϕ + α = qβ + 4 …(i)
2ϕ + 1 = 3q + 6 …(i)
3ϕ + 1 = 3q + 7
for (ii) &(iii) ϕ = 1, q = −1
So, from (i) α + β = 3
Now, point of intersection is (α + 1, 3, 4)
It lies on the plane.
Hence, α = 5&β = −2

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