JCECE Engineering JCECE Engineering Solved Paper-2006

  • question_answer
    A plane which passes through the point \[(3,\,\,2,\,\,0)\] and the line\[\frac{x-3}{1}=\frac{y-6}{5}=\frac{z-4}{4}\]is:

    A) \[x-y+z=1\]                        

    B) \[x+y+z=5\]

    C) \[x+2y-z=1\]     

    D) \[2x-y+z=5\]

    Correct Answer: A

    Solution :

    Key Idea: If a plane contains a line, then the normal to the plane is perpendicular to the line. Any plane passing through (3, 2, 0) is                 \[a(x-3)+b(y-2)+c(z-0)=0\]           ... (i) It passes through\[(3,\,\,6,\,\,4)\] \[\therefore \]  \[0.a+4b+4c=0\]                               ... (ii) Normal to plane (i) is perpendicular to given line \[\therefore \]  \[a+5b+4c=0\]                                   ... (ii) On solving Eqs. (i) and (ii), we get                 \[\frac{a}{1}=\frac{b}{-1}=\frac{c}{1}=k\] So,          \[a=k,\,\,b=-k,\,\,c=k\] Putting the value of\[a,\,\,\,b,\,\,\,c\]in Eq. (i), we get                 \[x-y+z=1\] Note: In any line of a plane it has only one direction cosines and direction ratios may be more than one.


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