J & K CET Engineering J and K - CET Engineering Solved Paper-2009

  • question_answer
    The equation of the circle passing through the point \[(1,\,\,1)\] and through the points of intersection of the circles \[{{x}^{2}}+{{y}^{2}}=6\] and \[{{x}^{2}}+\text{ }{{y}^{2}}-6y+8=0\]is

    A)  \[{{x}^{2}}+{{y}^{2}}+3y-13=0\]

    B)  \[{{x}^{2}}+{{y}^{2}}-3y+1=0\]

    C)  \[{{x}^{2}}+{{y}^{2}}-3x+1=0\]

    D)  \[5{{x}^{2}}+5{{y}^{2}}+6y+16=0\]

    Correct Answer: B

    Solution :

    The required equation of circle is \[({{x}^{2}}+{{y}^{2}}-6)+\lambda ({{x}^{2}}+{{y}^{2}}-6y+8)=0\] ?.(i) It passes through \[(1,1)\]. \[\therefore \] \[(1+1-6)+\lambda (1+1-6+8)=0\] \[\Rightarrow \] \[-4+4\lambda =0\] \[\Rightarrow \] \[\lambda =1\] \[\therefore \] Required equation of circle is \[{{x}^{2}}+{{y}^{2}}-6+{{x}^{2}}+{{y}^{2}}-6y+8=0\] \[\Rightarrow \] \[2{{x}^{2}}+2{{y}^{2}}-6y+2=0\] \[\Rightarrow \] \[{{x}^{2}}+{{y}^{2}}-3y+1=0\]


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