Manipal Engineering Manipal Engineering Solved Paper-2010

  • question_answer
    The reflection of the point (2, -1, 3) in the plane\[3x-2y-z=9\]is

    A) \[\left( \frac{26}{7},\,\,\frac{15}{7},\,\,\frac{17}{7} \right)\]        

    B) \[\left( \frac{26}{7},\,\,\frac{-15}{7},\,\,\frac{17}{7} \right)\]

    C) \[\left( \frac{15}{7},\,\,\frac{26}{7},\,\,\frac{-17}{7} \right)\]

    D) \[\left( \frac{26}{7},\,\,\frac{17}{7},\,\,\frac{-15}{7} \right)\]

    Correct Answer: B

    Solution :

    By image formula,                 \[\frac{{{x}_{2}}-{{x}_{1}}}{a}=\frac{{{y}_{2}}-{{y}_{1}}}{b}=\frac{{{z}_{2}}-{{z}_{1}}}{c}\]                 \[=-\frac{2(a{{x}_{1}}+b{{y}_{1}}+c{{z}_{1}}+d)}{{{a}^{2}}+{{b}^{2}}+{{c}^{2}}}\] \[\Rightarrow \]               \[\frac{{{x}_{2}}-2}{3}=\frac{{{y}_{2}}+1}{-2}\,=\frac{{{z}_{2}}-3}{-1}\]                 \[=-2\frac{(6+2-3-9)}{9+4+1}\] \[\Rightarrow \]               \[\frac{{{x}_{2}}-2}{3}=\frac{{{y}_{2}}+1}{-2}=\frac{{{z}_{2}}-3}{-1}=\frac{-2(-4)}{14}\] \[\therefore \]  \[{{x}_{2}}=\frac{26}{7},\,\,{{y}_{2}}=\frac{-15}{7},\,\,{{z}_{2}}=\frac{17}{7}\]


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