CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2007

  • question_answer
    The straight line\[3x+4y-5=0\]and \[4x=3y+15\]intersect at the point P. On these lines the points Q and R are chosen so that PQ = PR. The slopes of the lines QR passing through (1, 2) are

    A)  \[-7,1/7\]                           

    B)  \[7,1/7\]

    C)  \[7,-1/7\]           

    D)         \[3,-1/3\]

    E)  \[-3,1/3\]

    Correct Answer: A

    Solution :

    The given equations are \[3x+4y-5=0\]                               ...(i) and        \[4x-3y-15=0\]             ... (ii) Since, there lines are perpendicular to each other, so\[\angle QPR\]is right angle and\[PQ=PR\]. Hence,\[\Delta PQR\]is a right angle isosceles triangle. \[\therefore \]  \[\angle PQR=\angle PRQ=45{}^\circ \] Slope of \[PQ=-\frac{3}{4}\] and slope of \[PR=\frac{4}{3}\] Let slope of \[QR\text{ }=m\] \[\therefore \]  \[\tan 45{}^\circ =\left| \frac{\frac{4}{3}-m}{1+\frac{4}{3}m} \right|\] \[\Rightarrow \]               \[m=\frac{1}{7},-7\]


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