JEE Main & Advanced AIEEE Solved Paper-2004

  • question_answer
    Let A (2, - 3) and B (- 2,1) be vertices of a\[\Delta ABC\] 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 :

    If\[A({{x}_{1}},{{y}_{1}}),B({{x}_{2}},{{y}_{2}}),C({{x}_{3}},{{y}_{3}})\]are the vertices of a triangle, then the coordinates of the   centroid   of   a   triangle   are\[\left( \frac{{{x}_{1}}+{{x}_{2}}+{{x}_{3}}}{3},\frac{{{y}_{1}}+{{y}_{2}}+{{y}_{3}}}{3} \right)\]. Let\[(x,\text{ }y)\]be the coordinates of vertex C and \[({{x}_{1}},\text{ }{{y}_{1}})\]be the coordinates of centroid of the triangle. \[\therefore \]  \[{{x}_{1}}=\frac{x+2-2}{3}\]and\[{{y}_{1}}=\frac{y-3+1}{3}\] \[\Rightarrow \]               \[{{x}_{1}}=\frac{x}{3}\]and\[{{y}_{1}}=\frac{y-2}{3}\]                    ?.(i) Since, the centroid lies on the line\[2x+3y=1\]. So,\[{{x}_{1}}\]and\[{{y}_{1}}\]will satisfy the equation of line. \[\therefore \]  \[2{{x}_{1}}+3{{y}_{1}}=1\] \[\Rightarrow \]\[\frac{2x}{3}+\frac{3(y-2)}{3}=1\]                          [from Eq. (i)] \[\Rightarrow \]\[2x+3y-6=3\] \[\Rightarrow \]\[2x+3y=9\] This equation is locus of the vertex C.


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