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

  • question_answer
    A circle has radius 3 units and its centre lies on the line \[y=x-1\]. Then the equation of this circle if it passes through point (7,3), is [Roorkee 1988]

    A)            \[{{x}^{2}}+{{y}^{2}}-8x-6y+16=0\]

    B)            \[{{x}^{2}}+{{y}^{2}}+8x+6y+16=0\]

    C)            \[{{x}^{2}}+{{y}^{2}}-8x-6y-16=0\]

    D)            None of these

    Correct Answer: A

    Solution :

               Let its centre be (h, k), then \[h-k=1\]  ... (i)                    Also radius \[a=3\]                    Equation is \[{{(x-h)}^{2}}+{{(y-k)}^{2}}=9\]                    Also it passes through (7, 3)                    i.e., \[{{(7-h)}^{2}}+{{(3-k)}^{2}}=9\]                                    ?.(ii)                    We get h and k from (i) and (ii) solving simultaneously as (4, 3). Equation is \[{{x}^{2}}+{{y}^{2}}-8x-6y+16=0\].                    Trick : Since the circle \[{{x}^{2}}+{{y}^{2}}-8x-6y+16=0\] satisfies the given conditions.


You need to login to perform this action.
You will be redirected in 3 sec spinner