JEE Main & Advanced Mathematics Circle and System of Circles Question Bank Equations of circle, Geometrical problems regarding circle

  • question_answer
    The equations of the circles touching both the axes and passing through the point (1, 2) are

    A)            \[{{x}^{2}}+{{y}^{2}}-2x-2y+1=0,\ {{x}^{2}}+{{y}^{2}}-10x-10y+25=0\]

    B)            \[{{x}^{2}}+{{y}^{2}}-2x-2y-1=0,\ {{x}^{2}}+{{y}^{2}}-10x-10y-25=0\]

    C)            \[{{x}^{2}}+{{y}^{2}}+2x+2y+1=0,\ {{x}^{2}}+{{y}^{2}}+10x+10y+25=0\]

    D)            None of these

    Correct Answer: A

    Solution :

               Equation of circle touching both the axes will be \[{{x}^{2}}+{{y}^{2}}-2ax-2ay+{{a}^{2}}=0\]                    Also it passes through (1, 2), therefore \[a=5,\ 1\].                    Hence the equations of circles are                           \[{{x}^{2}}+{{y}^{2}}-2x-2y+1=0\]                    and \[{{x}^{2}}+{{y}^{2}}-10x-10y+25=0\].


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