Question:

Consider the lines \[ L_1: 2x+3y+1=0 \] and \[ L_2: 3x-2y+1=0. \] The locus of a variable point that is equidistant from the two lines \(L_1=0\) and \(L_2=0\) is

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The locus of points equidistant from two intersecting lines is the pair of angle bisectors. Using the distance formula and squaring both sides directly gives the combined equation of the two bisectors.
Updated On: Jul 29, 2026
  • \[ 5x^2-24xy-5y^2+2x-10y=0 \]
  • \[ x-5y=0 \]
  • \[ 5x+y=0 \]
  • \[ 5x^2-24xy-5y^2=0 \]
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The Correct Option is A

Solution and Explanation

Concept: If a point \((x,y)\) is equidistant from two lines \[ a_1x+b_1y+c_1=0 \] and \[ a_2x+b_2y+c_2=0, \] then \[ \frac{|a_1x+b_1y+c_1|} {\sqrt{a_1^2+b_1^2}} = \frac{|a_2x+b_2y+c_2|} {\sqrt{a_2^2+b_2^2}}. \] Squaring both sides gives the required locus.

Step 1: Write the distance condition. Given lines \[ L_1:2x+3y+1=0, \] \[ L_2:3x-2y+1=0. \] Since \[ \sqrt{2^2+3^2} = \sqrt{13} \] and \[ \sqrt{3^2+(-2)^2} = \sqrt{13}, \] the condition of equal distances becomes \[ |2x+3y+1| = |3x-2y+1|. \]

Step 2: Square both sides. \[ (2x+3y+1)^2 = (3x-2y+1)^2. \] Using \[ a^2-b^2=(a-b)(a+b), \] we get \[ [(2x+3y+1)-(3x-2y+1)] [(2x+3y+1)+(3x-2y+1)] =0. \] \[ (-x+5y)(5x+y+2)=0. \]

Step 3: Expand the product. \[ (-x+5y)(5x+y+2)=0. \] \[ -5x^2+24xy+5y^2-2x+10y=0. \] Multiplying throughout by \(-1\), \[ 5x^2-24xy-5y^2+2x-10y=0. \]

Step 4: Write the final answer. \[ \boxed{ 5x^2-24xy-5y^2+2x-10y=0 } \]
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