JEE Main & Advanced Sample Paper JEE Main - Mock Test - 30

  • question_answer
    The distance of the point (1, -2, 3) from the plane \[x-y+z=5\] measured parallel to the line\[\frac{x}{2}=\frac{y}{3}=\frac{z-1}{-6}\]is

    A) 1           

    B) 2

    C) 4                     

    D) none of these

    Correct Answer: A

    Solution :

    [a] : The equation of the line passing through \[P\left( 1,-2,3 \right)\]and parallel to the given line is \[\frac{x-1}{2}=\frac{y+2}{3}=\frac{z-3}{-6}\] Suppose it meets the plane \[x-y+z=5\]at the point Q given by\[\frac{x-1}{2}=\frac{y+2}{3}=\frac{z-3}{-6}=\lambda \] i.e.,\[(2\lambda +1,3\lambda -2,-6\lambda +3)\] This lies on x - y + z = 5. Therefore, \[2\lambda +1-3\lambda +2-6\lambda +3=5\Rightarrow -7\lambda =-1\Rightarrow \lambda =\frac{1}{7}\]So, the co-ordinates of Q are (9/7, -11/7, 15/7). Hence, required distance \[=PQ=\sqrt{\frac{4}{49}+\frac{9}{49}+\frac{36}{49}}=1\].


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