Q35 / 105 · NTA Abhyas (JEE Main) 2020 · Mathematics · Three Dimensional Geometry

Consider the line L:x-12=y+1-3=z+108 and a family of planes P containing the line L. The member of the family of planes P which is situated at a maximum distance from A1,0,0 will be

  • Correct answer
    A
    x-2y-z=13
  • B
    x+2y-z=7
  • C
    2x+y-z=7
  • D
    x+2y-2z=13

Solution

Let the foot of the perpendicular from A1,0,0 to given line L=0 is B, then the required plane must be perpendicular to AB and contain the given line.
Any general point on the given line is B=2λ+1,-3λ-1,8λ-10
AB→=<2λ,-3λ-1,8λ-10>
∴AB→ is perpendicular to the given line
⇒22λ+-3-3λ-1+88λ-10=0
⇒4λ+9λ+3+64λ-80=0
⇒λ=1
So, the coordinates of point B are 3,-4,-2
Equation of the required plane is
2x-1-4y+1-2z+10=0
⇒2x-2-4y-4-2z-20=0
⇒2x-4y-2z-26=0
⇒x-2y-z=13

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

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