J & K CET Engineering J and K - CET Engineering Solved Paper-2008

  • question_answer
    If the line \[y=7x-25\]meets the circle \[{{x}^{2}}+{{y}^{2}}=25\]in the points A, B then the distance between A and B is

    A)  \[\sqrt{10}\]

    B)  \[10\]

    C)  \[5\sqrt{2}\]

    D)  \[5\]

    Correct Answer: C

    Solution :

    The intersection point of line \[y=7x-25\] and circle \[{{x}^{2}}+{{y}^{2}}=25\] is \[{{x}^{2}}+{{(7x-25)}^{2}}=25\] \[\Rightarrow \] \[50{{x}^{2}}-350x+600=0\] \[\Rightarrow \] \[{{x}^{2}}-7x+12=0\] \[\Rightarrow \] \[(x-3)(x-4)=0\] \[\Rightarrow \] \[x=3,\,x=4\] and \[y=-4,3\] \[\therefore \]  Coordinates of \[A(3,-4)\] and \[B(4,3)\] \[\therefore \] Length,  \[AB=\sqrt{{{(4-3)}^{2}}+{{(3+4)}^{2}}}\] \[=\sqrt{1+49}=5\sqrt{2}\]


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