A plane E is perpendicular to the two planes 2x – 2y + z = 0 and x – y + 2z = 4, and passes through the point P(1, -1, 1). If the distance of the plane E from the point Q(a, a, 2) is
then (PQ)2 is equal to
A plane E is perpendicular to the two planes 2x – 2y + z = 0 and x – y + 2z = 4, and passes through the point P(1, -1, 1). If the distance of the plane E from the point Q(a, a, 2) is then (PQ)2 is equal to
Option 1 -
9
Option 2 -
12
Option 3 -
21
Option 4 -
33
-
1 Answer
-
Correct Option - 3
Detailed Solution:First plane, P1 = 2x – 2y + z = 0,
normal vector
Second plane, P2 = x – y + 2z = 4,
normal vector
Plane perpendicular to P1 and P2 will have normal vector n3 where n3 = (n1 × n2)
Hence,
n3 = (3, 0)
Distance PQ
Similar Questions for you
....(1)
Let
Let
Put l1 and l2 in (1)
α = 3
Given , ,
Dot product with on both sides
... (1)
Dot product with on both sides
... (2)
(a – 1) × 2 + (b – 2) × 5 + (g – 3) × 1 = 0
2a + 5b + g – 15 = 0
Also, P lie on line
a + 1 = 2λ
b – 2 = 5λ
g – 4 = λ
2 (2λ – 1) + 5 (5λ + 2) + λ + 4 – 15 = 0
4λ + 25λ + λ – 2 + 10 + 4 – 15 = 0
30λ – 3 = 0
a + b + g = (2λ – 1) + (5λ + 2) + (λ + 4)

Take
x = 2λ + 1, y = 3λ + 2, z = 4λ + 3
= (α − 2)
Now,
(α − 2) ⋅ 2 + (β − 3) ⋅3 + (γ − 4) ⋅ 4 = 0
2α − 4 + 3β − 9 + 4γ −16 = 0
⇒ 2α + 3β + 4γ = 29
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