JAMIA MILLIA ISLAMIA Jamia Millia Islamia Solved Paper-2007

  • question_answer
        Let\[A(2,-3)\]and\[B(-2,1)\]be vertices of a triangle ABC. If the centroid of this triangle moves on the line\[2x+3y=1,\]then the locus of the vertex C is the line:

    A)  \[2x+3y=9\]      

    B)  \[2x-3y=7\]

    C)  \[3x+2y=5\]      

    D)  \[3x-2y=3\]

    Correct Answer: A

    Solution :

                    Let\[(x,\text{ }y)\]be the co-ordinates of vertex C and \[({{x}_{1}},{{y}_{1}})\]be the co-ordinates of centroid of the triangle. \[\therefore \]  \[{{x}_{1}}=\frac{x+2-2}{3}\] \[{{y}_{1}}=\frac{y-3+1}{3}\] \[\Rightarrow \]               \[{{x}_{1}}=\frac{x}{3}\]and \[{{y}_{1}}=\frac{y-2}{3}\] Since the centroid lies on the line\[2x+3y=1\]. So,\[{{x}_{1}}\]and\[{{y}_{1}}\]satisfied the equation of line. \[\therefore \]  \[2{{x}_{1}}+3{{y}_{1}}=1\] \[\Rightarrow \]               \[\frac{2x}{3}+\frac{3(y-2)}{3}=1\] \[\Rightarrow \]               \[2x+3y-6=3\] \[\Rightarrow \]               \[2x+3y=9\] This equation is locus of the vertex C.


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