JEE Main & Advanced Mathematics Rectangular Cartesian Coordinates Question Bank Transformation of axes and Locus

  • question_answer
    If sum of distances of a point from the origin and lines \[x=2\] is 4, then its locus is       [RPET 1997]

    A) \[{{x}^{2}}-12y=36\]

    B) \[{{y}^{2}}+12x=36\]

    C) \[{{y}^{2}}-12x=36\]

    D) \[{{x}^{2}}+12y=36\]

    Correct Answer: B

    Solution :

    Let point be \[P\,(x,\,\,y)\]. So, distance from the origin \[OP=\sqrt{{{x}^{2}}+{{y}^{2}}}\] and distance from the line \[=(x-2)\] \[\therefore \,\,\,\sqrt{{{x}^{2}}+{{y}^{2}}}+(x-2)=4\,\,\,\Rightarrow \,\,\sqrt{{{x}^{2}}+{{y}^{2}}}=(-x+6)\] \[\Rightarrow \,\,{{x}^{2}}+{{y}^{2}}={{x}^{2}}+36-12x\,\,\Rightarrow \,\,{{y}^{2}}+12x=36\].


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