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QJEEM15Mabc7e: JEE Main 2015 Mathematics - Class 11 JEEM15Mabc7e Solution: Locus of the image of the point in the line is a :

Locus of the image of the point (2,3)(2, 3) in the line (2x−3y+4)+k(x−2y+3)=0, k∈R,\left( {2x - 3y + 4} \right) + k\left( {x - 2y + 3} \right) = 0,\,k \in R, is a :

Multiple Choice Options

  • A circle of radius 2\sqrt 2 .
  • B circle of radius 3\sqrt 3 .
  • C straight line parallel to xx -axis
  • D straight line parallel to yy -axis

Step-by-Step Verified Solution

Intersection point of 2x−3y+4=02x - 3y + 4 = 0

and x−2y+3=0x-2y+3=0 is (1,2)(1, 2)

JEE Main 2015 (Offline) Mathematics - Circle Question 142 English Explanation
Since, PP is the fixed point for given family of lines

So, PB=PAPB=PA

(α−1)2+(β−2)2=(2−1)2+(3−2)2{\left( {\alpha - 1} \right)^2} + {\left( {\beta - 2} \right)^2} = {\left( {2 - 1} \right)^2} + {\left( {3 - 2} \right)^2}

(α−1)2+(β−2)2=1+1=2{\left( {\alpha - 1} \right)^2} + {\left( {\beta - 2} \right)^2} = 1 + 1 = 2

(x−1)2+(y−2)2=(2)2{\left( {x - 1} \right)^2} + {\left( {y - 2} \right)^2} = {\left( {\sqrt 2 } \right)^2}

(x−a)2+(y−b)2=r2{\left( {x - a} \right)^2} + {\left( {y - b} \right)^2} = {r^2}

Therefore, given locus is a circle with center (1,2)(1, 2) and radius 2.\sqrt 2 .

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