JEE Main & Advanced JEE Main Paper Phase-I (Held on 08-1-2020 Evening)

  • question_answer
    The mirror image of the point (1, 2, 3) in a plane is \[\left( -\frac{7}{3},-\frac{4}{3},-\frac{1}{3} \right)\]. Which of the following points lies on this plane? [JEE MAIN Held on 08-01-2020 Evening]

    A) \[\left( -1,-1,-1 \right)\]     

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

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

    D) \[\left( 1,-1,\,\,1 \right)\]

    Correct Answer: D

    Solution :

    Let \[A\,\,(1,\,2,\,3),\,\,\,B\left( \frac{-7}{3},\frac{-4}{3},\frac{-1}{3} \right)\] Mid-point of \[AB\equiv \left( \frac{-2}{3},\frac{1}{3},\frac{4}{3} \right)\] Let equation of plane is \[a\left( x+\frac{2}{3} \right)+b\left( y-\frac{1}{3} \right)+c\left( z-\frac{4}{3} \right)=0\]     ... (i) dr's of \[AB=\frac{10}{3},\frac{10}{3},\frac{10}{3}\] \[\therefore \]    Equation of plane is        \[x+\frac{2}{3}+y-\frac{1}{3}+z-\frac{4}{3}=0\] \[\Rightarrow \,\,\,\,\,x+y+z=1\] \[\therefore \] (1, -1, +1) lies on the plane


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