JEE Main & Advanced Sample Paper JEE Main Sample Paper-14

  • question_answer
    The distance between a point with position vector \[5i+j+3k\] and the line \[r=(3i+7j+k)+\lambda (j+k)\] is

    A)  10                                         

    B)  9                

    C)  7                                            

    D)  6

    Correct Answer: D

    Solution :

     Given equation of the line is \[\frac{x-3}{0}=\frac{y-7}{1}=\frac{z-1}{1}=(k)\] (say) Any point on the line is \[(3,\,7+k,\,1+k)\] The line joining \[A(5,\,\,1,\,\,3)\] and \[B(3,\,7+k,\,\,1+k)\] is perpendicular to the given line if \[0\,(-2)\,+\,(6+k)\cdot \,(1)\,+(k-2)\,\cdot \,(1)=0\] \[\Rightarrow \]               \[6+k+k-2=0\] \[\Rightarrow \]               \[2k+4=0\] \[\Rightarrow \]               \[k=-2\] \[\therefore \] Any point B(3, 5, - 1) lie on the line. \[\therefore \] Required distance \[AB=\sqrt{{{2}^{2}}+{{4}^{2}}+{{4}^{2}}}\] \[=\sqrt{36}=6\]


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