JCECE Engineering JCECE Engineering Solved Paper-2015

  • question_answer
    Equation of plane passing through the points\[(2,\,\,2,\,\,1)\],\[(9,\,\,3,\,\,6)\] and perpendicular to the plane \[2x+6y+6z-1=0\], is

    A) \[3x+4y+5z=9\]

    B) \[3x+4y-5z+9=0\]

    C) \[3x+4y-5z-9=0\]

    D)  None of these

    Correct Answer: C

    Solution :

    Equation of a plane passing through \[(2,\,\,2,\,\,1)\] is                 \[a(x-2)+b(y-2)+c(z-1)=0\]           ... (i) This passes through \[(9,\,\,3,\,\,6)\] and is perpendicular to                 \[2x+6y+6z-1=0\] \[\therefore \]  \[7a+b+5c=0\] and        \[2a+6b+6c=0\] On solving above equations by cross-multiplication, we get \[\Rightarrow \]               \[\frac{a}{6-30}=\frac{-b}{42-10}=\frac{c}{42-2}\] \[\Rightarrow \]               \[\frac{a}{-24}=\frac{b}{-32}=\frac{c}{40}\] \[\Rightarrow \]               \[\frac{a}{-3}=\frac{b}{-4}=\frac{c}{5}\] On substituting the values of \[a,\,\,b\] and \[c\] in Eq. (i), we get                 \[-3(x-2)-4(y-2)+5(z-1)=0\] or \[3x+4y-5z-9=0\] as the required plane.


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