JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2006

  • question_answer
        The equation of the circle passing through (4,5) having the centre (2, 2) is

    A) \[{{x}^{2}}+{{y}^{2}}+4x+4y-5=0\]

    B)  \[{{x}^{2}}+{{y}^{2}}-4x-4y-5=0\]

    C)  \[{{x}^{2}}+{{y}^{2}}-4x=13\]

    D)  \[{{x}^{2}}+{{y}^{2}}-4x-4y+5=0\]

    Correct Answer: B

    Solution :

                    Key Idea: Equation of circle with centre (h, k) and radius r is\[{{(x-h)}^{2}}+{{(y-k)}^{2}}={{r}^{2}}\]. Since, circle passes through (4, 5) and centre is (2, 2). \[\therefore \]Radius \[=\sqrt{{{(4-2)}^{2}}+{{(5-2)}^{2}}}=\sqrt{4+9}=\sqrt{13}\] \[\therefore \]Equation of circle                 \[{{(x-2)}^{2}}+{{(y-2)}^{2}}={{(\sqrt{13})}^{2}}\] \[\Rightarrow \] \[{{x}^{2}}+{{y}^{2}}-4x-4y+4+4-13=0\] \[\Rightarrow \]        \[{{x}^{2}}+{{y}^{2}}-4x-4y-5=0\]


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