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

  • question_answer
    The two circles \[{{x}^{2}}+{{y}^{2}}-2x+22y+5=0\] and \[{{x}^{2}}+{{y}^{2}}+14x+6y+k=0\] intersect orthogonally provided k is equal to [Karnataka CET 2005]

    A)          47  

    B)             \[-47\]

    C)             49  

    D)             \[-\text{ }49\]

    Correct Answer: A

    Solution :

               Given two circles                    \[{{x}^{2}}+{{y}^{2}}-2x+22y+5=0\]                    \[{{x}^{2}}+{{y}^{2}}+14x+6y+k=0\]                    The two circles cut orthogonally, if                    \[2({{g}_{1}}{{g}_{2}}+{{f}_{1}}{{f}_{2}})={{c}_{1}}+{{c}_{2}}\]i.e., \[2(-1.7+11.3)=5+k\]                     \[2(-7+33)=5+k\Rightarrow 52-5=k\Rightarrow k=47\].


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