VIT Engineering VIT Engineering Solved Paper-2009

  • question_answer
    The area (in square unit) of the triangle formed by\[x+y+1=0\] and the pair of straight lines\[{{x}^{2}}-3xy+2{{y}^{2}}=0\]is

    A)  \[\frac{7}{12}\]

    B)  \[\frac{5}{12}\]

    C)  \[\frac{1}{12}\]

    D)  \[\frac{1}{6}\]

    Correct Answer: C

    Solution :

    Given,  \[{{x}^{2}}-2xy-xy+2{{y}^{2}}=0\] \[\Rightarrow \] \[(x-2y)\,(x-y)=0\] \[\Rightarrow \] \[x=2y,\] \[x=y\] ?(i) Also,     \[x+y+1=0\]           ...(ii) On solving Eqs. (i) and (ii), we get \[A\left( -\frac{2}{3},\,-\frac{1}{3} \right),\]\[B\left( -\frac{1}{2},\,-\frac{1}{2} \right),\,C(0,\,0)\] \[\therefore \]Area of \[\Delta \,ABC=\frac{1}{2}\left| \,\begin{matrix}    -\frac{2}{3} & -\frac{1}{3} & 1  \\    -\frac{1}{2} & -\frac{1}{2} & 1  \\    0 & 0 & 1  \\ \end{matrix}\, \right|\] \[=\frac{1}{2}\left[ \frac{1}{3}-\frac{1}{6} \right]=\frac{1}{2}\left[ \frac{1}{6} \right]=\frac{1}{12}\]


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