Q16 / 105 · NTA Abhyas (JEE Main) 2020 · Mathematics · Three Dimensional Geometry

If ax+13y+bz+c=0 is a plane through the line of intersection of 2x+3y-z+1=0, x+y-2z+3=0 and is perpendicular to the plane 3x-y-2z=4, then the value of 2a+3b+4c is equal to

  • A
    -12
  • B
    12
  • C
    10
  • Correct answer
    D
    -10

Solution

Equation of the plane through the line of intersection of given 2 planes is
2x+3y-z+1+λx+y-2z+3=0
2+λx+3+λy-1+2λz+1+3λ=0
∵ it is perpendicular to 3x-y-2z=4
6+3λ-3-λ+4λ+2=0
6λ+5⇒λ=-56
7x+13y+4z-9=0
On comparing a=7,b=4,c=-9

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

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