JEE Main & Advanced Mathematics Rectangular Cartesian Coordinates Question Bank Questions related to geometrical conditions

  • question_answer
    The points \[(-a,-b),\ (a,b),\ ({{a}^{2}},ab)\]are

    A) Vertices of an equilateral triangle

    B) Vertices of a right angled triangle

    C) Vertices of an isosceles triangle

    D) Collinear

    Correct Answer: D

    Solution :

    \[{{l}_{1}}=\sqrt{{{(2a)}^{2}}+{{(2b)}^{2}}}=2\sqrt{{{a}^{2}}+{{b}^{2}}}\] \[{{l}_{2}}=\sqrt{{{({{a}^{2}}-a)}^{2}}+{{b}^{2}}{{(a-1)}^{2}}}=(a-1)\,\sqrt{{{a}^{2}}+{{b}^{2}}}\] \[{{l}_{3}}=\sqrt{{{({{a}^{2}}+a)}^{2}}+{{b}^{2}}{{(a+1)}^{2}}}=(a+1)\,\sqrt{{{a}^{2}}+{{b}^{2}}}\] Now \[{{l}_{1}}+{{l}_{2}}={{l}_{3}}.\] Hence points are collinear.


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