Q44 / 109 · NTA Abhyas (JEE Main) 2020 · Mathematics · Straight Lines

Let the images of the point A2,3 about the lines y=x and y=mx are P and Q respectively. If the line PQ passes through the origin, then m is equal to

  • A
    32
  • B
    23
  • Correct answer
    C
    -1
  • D
    5

Solution

Figure
Reflection of A2,3 about line y=x is 3,2=P
Equation of the line PQ is the same as line OP
⇒ equation of the line PQ is y=23x and the equation of the line OA is y=32x.
Now, y=mx & y=x are the angle bisectors of the lines 2x-3y=0 and 3x-2y=0
Now, angle bisectors of 2x-3y=0 and 3x-2y=0 are y=x and y=-x
⇒m=-1

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

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