J & K CET Engineering J and K - CET Engineering Solved Paper-2004

  • question_answer
    If the normal to the parabola \[{{x}^{2}}=-4ay\] at the points \[({{x}_{1}},\,{{y}_{1}}),\,({{x}_{2}},{{y}_{2}})\] and \[({{x}_{3}},{{y}_{3}})\] are concurrent, then

    A)  \[{{y}_{1}}+{{y}_{2}}+{{y}_{3}}=0\]

    B)  \[{{x}_{1}}{{x}_{2}}+{{x}_{2}}{{x}_{2}}+{{x}_{3}}{{x}_{1}}=0\]

    C)  \[{{x}_{1}}+{{x}_{2}}+{{x}_{3}}=0\]

    D)  \[{{x}_{1}}{{y}_{1}}+{{x}_{2}}{{y}_{2}}+{{x}_{3}}{{y}_{3}}=0\]

    Correct Answer: A

    Solution :

    If the normal to the parabola \[{{x}^{2}}=-4ay\] at the points \[({{x}_{1}},{{y}_{1}}),\,({{x}_{2}},{{y}_{2}})\] and \[({{x}_{3}},{{y}_{3}})\]are concurrent, then sum of ordinate is zero. ie, \[{{y}_{1}}+{{y}_{2}}+{{y}_{3}}=0\]


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