JCECE Engineering JCECE Engineering Solved Paper-2008

  • question_answer
    On the parabola \[y={{x}^{2}}\], the point least distance from the straight line \[y=2x-4\] is

    A) \[(1,\,\,1)\]                                        

    B) \[(1,\,\,0)\]

    C) \[(1,\,\,-1)\]                      

    D) \[(0,\,\,0)\]

    Correct Answer: A

    Solution :

    Given, parabola is\[y={{x}^{2}}\]                              ... (i) and straight line\[y=2x-4\]                           ... (ii) From Eqs. (i) and (ii),\[{{x}^{2}}-2x+4=0\] Let          \[f(x)={{x}^{2}}-2x+4\] On differentiating w.r.t.\[x,\] we get                 \[f'(x)=2x-2\] For least distance,\[f'(x)=0\] \[\Rightarrow \]               \[2x-2=0\] \[\Rightarrow \]                       \[x=1\] On putting \[x=1\] in Eq. (i), we get                         \[y=1\] Hence, the point least distance from the line is\[(1,\,\,1)\].


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