JEE Main & Advanced Mathematics Circle and System of Circles Question Bank System of circles

  • question_answer
    The equation of circle which passes through the point (1,1) and intersect the given circles \[{{x}^{2}}+{{y}^{2}}+2x+4y+6=0\] and \[{{x}^{2}}+{{y}^{2}}+4x+6y+2=0\] orthogonally, is

    A)            \[{{x}^{2}}+{{y}^{2}}+16x+12y+2=0\]                      

    B)            \[{{x}^{2}}+{{y}^{2}}-16x-12y-2=0\]

    C)            \[{{x}^{2}}+{{y}^{2}}-16x+12y+2=0\]                        

    D)            None of these

    Correct Answer: C

    Solution :

                Let equation of circle be\[{{x}^{2}}+{{y}^{2}}+2gx+2fy+c=0\].                    As it intersects orthogonally the given circles, we have \[2g+4f=6+c\] and \[4g+6f=2+c\].                    As it passes through (1, 1), we have \[2g+2f=-2-c\]                    From these, we get \[g,\ f\] and c as ?8, 6, 2 respectively and hence equation of circle as                     \[{{x}^{2}}+{{y}^{2}}-16x+12y+2=0\].


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