CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2004

  • question_answer
    What is the equation of the locus of a point which moves such that 4 times its distance from the x-axis is the square of its distance from the origin?

    A)  \[{{x}^{2}}+{{y}^{2}}-4y=0\]      

    B)  \[{{x}^{2}}+{{y}^{2}}-4|y|=0\]

    C)  \[{{x}^{2}}+{{y}^{2}}-4x=0\]      

    D)  \[{{x}^{2}}+{{y}^{2}}-4|x|=0\]

    Correct Answer: B

    Solution :

    Let \[(h,\,k)\] be the point. According to question                 \[4\,\sqrt{{{(h-h)}^{2}}+{{k}^{2}}}={{h}^{2}}+{{k}^{2}}\] \[\Rightarrow \]               \[4\,\,\left| k \right|={{h}^{2}}+{{k}^{2}}\] Locus of the point is \[\Rightarrow \]               \[4\,\,\left| y \right|={{x}^{2}}+{{y}^{2}}\] \[\Rightarrow \]               \[{{x}^{2}}+{{y}^{2}}-4\,\left| y \right|=0\]


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