CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2009

  • question_answer
    For the parabola \[{{y}^{2}}=4x,\]the point P whose focal distance is 17, is

    A)  \[(8,8)\] or \[(8,-8)\]

    B)  \[(4,8)\] or \[(4,-8)\]

    C)  \[(2,8)\] or \[(2,-8)\]

    D)  \[(16,8)\] or \[(16,-8)\]

    Correct Answer: D

    Solution :

    Given, \[{{y}^{2}}=4x\] Let \[P(h,k)\] be any point on the parabola \[\therefore \]  \[{{(h-1)}^{2}}+{{(k-0)}^{2}}={{17}^{2}}\] Alos,      \[{{k}^{2}}=4h\] \[\therefore \]  \[{{h}^{2}}+1-2h+4h=289\] \[\Rightarrow \]               \[{{h}^{2}}+2h--288=0\] \[\Rightarrow \]               \[(h+18)\,(h-16)=0\] \[\Rightarrow \]               \[h=16\] ( \[\because \] h cannot be negative) \[\therefore \]  \[{{k}^{2}}=64\]                 \[\Rightarrow \]               \[k=\pm 8\]                 \[\therefore \]   Points are \[(16,8)\] or \[(16,-8)\],


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