JEE Main & Advanced Sample Paper JEE Main - Mock Test - 40

  • question_answer
    The variable plane \[(2\lambda +1)x+(3-\lambda )y+z=4,\]\[(\lambda \in R)\] always contains the line

    A) \[\frac{x}{0}=\frac{y}{0}=\frac{z+4}{1}\]

    B)        \[\frac{x}{1}=\frac{y}{2}=\frac{z}{-3}\]

    C) \[\frac{x}{1}=\frac{y}{2}=\frac{z-4}{-7}\]

    D)        None of these

    Correct Answer: C

    Solution :

    [c] Given plane is \[(2\lambda +1)x+(3-\lambda )y+z=4,(\lambda \in R)\] Or  \[\lambda (2x-y)+x+3y+z-4=0\] This is family of planes containing the line of intersection of planes \[{{P}_{1}}:x+3y+z-4=0\] and \[{{P}_{2}}:2x-y=0\]. Let  \[x=\alpha .\] \[\therefore \,\,\,\,\,\,y=2\alpha \] and \[z=4-7\alpha \] Thus, one of the lines on the plane is \[\frac{x}{1}=\frac{y}{2}=\frac{z-4}{-7}.\]


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