Q20 / 105 · NTA Abhyas (JEE Main) 2020 · Mathematics · Three Dimensional Geometry

Distance between two non-intersecting planes P1 and P2 is 5 units, where P1 is 2x-3y+6z+26=0 and P2 is 4x+by+cz+d=0. The point A-3,0,-1 lies between the planes P1 and P2, then the value of 3b+4c-5d is equal to

  • A
    580
  • Correct answer
    B
    120
  • C
    -18
  • D
    -120

Solution

Since both the planes are parallel
P1:4x-6y+12z+52=0
P2:4x-6y+12z+d=0
Therefore, d-5214=5⇒d-52=70
⇒d=122,-18
∴P2 is 4x-6y+12z+122=0 or
4x-6y+12z-18=0
Since the point -3,0,-1 is lying between P1 and P2
∴ On substituting the point in both the equations of the plane, both the expressions must be of opposite signs
Hence, 4x-6y+12z-18=0 is the equation of the required plane

Hence, the correct answer is option: 'B'.

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