J & K CET Engineering J and K - CET Engineering Solved Paper-2005

  • question_answer
    The image of the point \[P(1,3,4)\] in the plane \[2x-y+z+3=0\] is

    A)  \[(3,\,5,-2)\]     

    B)  \[(-3,\,5,2)\]

    C)  \[(3,-5,2)\]     

    D)  \[(-1,\,4,2)\]

    Correct Answer: B

    Solution :

    The image of the point \[({{x}_{1}},{{y}_{1}},{{z}_{1}})\] in the plane  \[ax+by+cz+d=0\]is \[\frac{x-{{x}_{1}}}{a}=\frac{y-{{y}_{1}}}{b}=\frac{z-{{z}_{1}}}{c}\] \[=\frac{-2(a{{x}_{1}}+b{{y}_{1}}+c{{z}_{1}}+d)}{{{a}^{2}}+{{b}^{2}}+{{c}^{2}}}\] \[\therefore \]\[\frac{x-1}{2}=\frac{y-3}{-1}=\frac{z-4}{1}=-2\left( \frac{2-3+4+3}{6} \right)\] \[\Rightarrow \]  \[z=-3,\,y=5\] and \[z=2\] \[\therefore \] image of the point is \[(-3,5,2)\].


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