CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2009

  • question_answer
    If the lines\[y=3x+1\]and\[2y=x+3\]are equally inclined to the line\[y=mx+4,\left( \frac{1}{2}<m<3 \right),\]then the values of m are

    A)  \[\frac{1}{7}(1\pm 5\sqrt{3})\]                

    B)  \[\frac{1}{7}(1\pm 5\sqrt{5})\]

    C)  \[\frac{1}{7}(1\pm 5\sqrt{2})\]

    D)         \[\frac{1}{7}(1\pm 2\sqrt{5})\]

    E)  \[\frac{1}{7}(1\pm 3\sqrt{2})\]

    Correct Answer: C

    Solution :

    As \[m\in \left( \frac{1}{2},3 \right)\] \[\therefore \]Line\[y=mx+4\]lies between \[y=3x+1\]and\[2y=x+3\] Slopes of given lines are\[{{m}_{2}}=3,m=m\]and\[{{m}_{1}}=\frac{1}{2}\] \[\therefore \]  \[\tan \theta =\frac{3-m}{1+3m}\] and        \[\tan \theta =\frac{m-\frac{1}{2}}{1+\frac{m}{2}}\] \[\Rightarrow \]               \[\frac{3-m}{1+3m}=\frac{2m-1}{2+m}\] \[\Rightarrow \]               \[7{{m}^{2}}-2m-7=0\] \[\therefore \,\,\,m=\frac{2\pm \,\sqrt{4+196}}{2\times 7}\,=\frac{1}{7}\,(1\pm \,5\sqrt{2})\]


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