JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2007

  • question_answer
        The intercept on the line\[y=x\]by the circle \[{{x}^{2}}+{{y}^{2}}-2x=0\]is AB, Equation of the circle on AB as a diameter is

    A)  \[{{x}^{2}}+{{y}^{2}}-x-y=0\]

    B)  \[{{x}^{2}}+{{y}^{2}}-x+y=0\]

    C)  \[{{x}^{2}}+{{y}^{2}}+x+y=0\]

    D)  \[{{x}^{2}}+{{y}^{2}}+x-y=0\]

    Correct Answer: A

    Solution :

                    The equation of line is\[y=x\]             ...(i) and equation of circle is \[{{x}^{2}}+{{y}^{2}}-2x=0\]                  ...(ii) On solving Eqs. (i) and (ii), we get \[\Rightarrow \]               \[{{x}^{2}}+{{x}^{2}}-2x=0\] \[\Rightarrow \]               \[2{{x}^{2}}-2x=0\] \[\Rightarrow \]               \[2x(x-1)=0\] \[\Rightarrow \]               \[x=0,\text{ }x=1\] when \[x=0,\text{ }y=0\] when \[x=1,\text{ }y=1\] Let co-ordinates of A are (0, 0) and co-ordinates of B are (1, 1). \[\therefore \]Equation of circle (AB as a diameter) is \[(x-{{x}_{1}})(x-{{x}_{2}})+(y-{{y}_{1}})(y-{{y}_{2}})=0\] \[\Rightarrow \]               \[(x-0)(x-1)+(y-0)(y-1)=0\] \[\Rightarrow \]               \[x(x-1)+y(y-1)=0\] \[\Rightarrow \]               \[{{x}^{2}}-x+{{y}^{2}}-y=0\] \[\Rightarrow \]               \[{{x}^{2}}+{{y}^{2}}-x-y=0\]


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