Manipal Engineering Manipal Engineering Solved Paper-2012

  • question_answer
    The mid-point of the line joining the common points of the line\[2x-3y+8=0\]and\[{{y}^{2}}=8x\]is

    A) \[(3,\,\,2)\]                        

    B) \[(5,\,\,6)\]

    C) \[(4,\,\,-1)\]      

    D)        \[(2,\,\,-3)\]

    Correct Answer: B

    Solution :

    Let\[({{x}_{1}},\,\,{{y}_{1}})\]be the mid-point of the line joining the common points of the given line and the given parabola. Then, the equation of line is                 \[y{{y}_{1}}-4(x+{{x}_{1}})=y_{1}^{2}-8{{x}_{1}}\] \[\Rightarrow \]               \[4x-y{{y}_{1}}+y_{1}^{2}-4{{x}_{1}}=0\] This line and\[2x-3y+8=0\]represents the same line. \[\therefore \]  \[\frac{4}{2}=\frac{-{{y}_{1}}}{-3}=\frac{y_{1}^{2}-4{{x}_{1}}}{8}\] \[\Rightarrow \]               \[{{y}_{1}}=6,\,\,y_{1}^{2}-4{{x}_{1}}=16\] \[\Rightarrow \]               \[{{y}_{1}}=6,\,\,{{x}_{1}}=\frac{36-16}{4}\] \[\Rightarrow \]               \[{{y}_{1}}=6,\,\,{{x}_{1}}=5\] \[\therefore \]The required point is (5, 6).


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