J & K CET Engineering J and K - CET Engineering Solved Paper-2014

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

    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: B

    Solution :

    Given, equation of line is \[y=x\] ?.(i) and equation of a circle is \[{{x}^{2}}+{{y}^{2}}-2x=0\] ?(ii) on putting the value of y from Eq. (i) in Eq. (ii), we get \[{{x}^{2}}+{{x}^{2}}-2x=0\] \[\Rightarrow \] \[2x(x-1)=0\] \[\Rightarrow \] \[x=0,1\] Then from Eq. (i), we get \[y=0,1\] Let \[A=(0,0)\] and \[B=(1,1)\] Now, equation of circle o AB as a diameter is \[(x-0)(x-1)+(y-0)(y-1)=0\] \[\Rightarrow \] \[x(x-1)+y(y-1)=0\] \[\Rightarrow \] \[{{x}^{2}}+{{y}^{2}}-x-y=0\]


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