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

  • question_answer
    The equation of the circle passing through the points (0, 0), (0, b) and (a, b) is                                           [AMU 1978]

    A)            \[{{x}^{2}}+{{y}^{2}}+ax+by=0\]                                

    B)            \[{{x}^{2}}+{{y}^{2}}-ax+by=0\]

    C)            \[{{x}^{2}}+{{y}^{2}}-ax-by=0\]                                    

    D)            \[{{x}^{2}}+{{y}^{2}}+ax-by=0\]

    Correct Answer: C

    Solution :

               Equation of circle passing through (0, 0) is                    \[{{x}^{2}}+{{y}^{2}}+2gx+2fy=0\]                                         ?.(i)                    Also, circle (i) is passing through (0, b) and (a, b)                    \[\therefore \]\[f=-\frac{b}{2}\] and \[{{a}^{2}}+{{b}^{2}}+2ag+2\text{ }\left( -\frac{b}{2} \right)\text{  }b=0\]                    \[\Rightarrow g=-\frac{a}{2}\]                    Hence the equations of circle is, \[{{x}^{2}}+{{y}^{2}}-ax-by=0\].


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