Q43 / 105 · NTA Abhyas (JEE Main) 2020 · Mathematics · Three Dimensional Geometry

Consider a plane P:2x+y-z=5, a line L:x-32=y+1-3=z-2-1 and a point A3,-4,1. If the line L intersects plane P at B and the xy plane at C, then the area (in sq. units) of ∆ABC is

  • A
    7
  • B
    8
  • Correct answer
    C
    10
  • D
    23

Solution

For xy plane, putting z=0, we get,
x-32=y+1-3=2⇒x=7,y=-7
Coordinates of point C are 7,-7,0
Any general point on the line is 2λ+3,-3λ-1,-λ+2
This must satisfy the given plane
4λ+6-3λ-1+λ-2=5
2λ+3=5⇒λ=1
So, coordinates of point B are 5,-4,1
AB→=<2,0,0>AC→=<4,-3,-1>
Area =12AB→×AC→=12i^j^k^2004-3-1
=12-2-j^+3k^=j^-3k^=10 sq. units

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

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