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

  • question_answer
    The equation of a circle that intersects the circle \[{{x}^{2}}+{{y}^{2}}+14x+6y+2=0\]orthogonally and whose centre is (0, 2) is [MP PET 1998]

    A)            \[{{x}^{2}}+{{y}^{2}}-4y-6=0\]                                      

    B)            \[{{x}^{2}}+{{y}^{2}}+4y-14=0\]

    C)            \[{{x}^{2}}+{{y}^{2}}+4y+14=0\]                                

    D)          \[{{x}^{2}}+{{y}^{2}}-4y-14=0\]

    Correct Answer: D

    Solution :

               In circle, \[{{x}^{2}}+{{y}^{2}}+14x+6y+2=0\]                    \[g=7,\ f=3,\ c=2\]                    Centre of circle\[(-g,\ -f)=(0,\ 2)\], (Given)                    For orthogonally intersection, \[2gg'+2ff'=c+c'\]                    \[0-12=2+c'\Rightarrow c'=-14\]                    Put the values, in equation\[{{x}^{2}}+{{y}^{2}}+2g'x+2f'x+c'=0\].                    \[\Rightarrow {{x}^{2}}+{{y}^{2}}+0-4y-14=0\Rightarrow {{x}^{2}}+{{y}^{2}}-4y-14=0\].


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