BCECE Engineering BCECE Engineering Solved Paper-2001

  • question_answer
    Two   lines   represented   by   equation \[{{x}^{2}}++xy+{{y}^{2}}=0\] are:

    A)  coincident                         

    B)  parallel

    C)  mutually perpendicular

    D)  imaginary

    Correct Answer: D

    Solution :

    Given pair of lines are \[{{x}^{2}}+xy+{{y}^{2}}=0\] This is a quadratic equation in \[x\]                 \[\therefore \]  \[x=\frac{-y\pm \sqrt{{{y}^{2}}-4{{y}^{2}}}}{2}=y\left( \frac{-1\pm \sqrt{3}i}{2} \right)\]                 \[\Rightarrow \]\[x=\omega y\]and \[x={{\omega }^{2}}y\] Where \[\omega ,{{\omega }^{2}}\]are the cube roots of unity \[\Rightarrow \]               \[(x-\omega y)(x-{{\omega }^{2}}y)=0\] \[\therefore \] The given lines are imaginary.


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