JEE Main & Advanced AIEEE Solved Paper-2002

  • question_answer
    If \[\left| \begin{matrix} 6\,i & -3\,i & 1  \\ 4 & 3\,i & -1  \\    20 & 3 & i  \\ \end{matrix} \right|=x+iy\], then   AIEEE  Solved  Paper-2002

    A) \[x=3,\,y=1\]

    B)                           \[x=1,\,y=3\]        

    C)           \[x=0,\,y=3\]        

    D)           \[x=0,\,y=0\]

    Correct Answer: D

    Solution :

    Now, \[\left| \begin{matrix}    6i & -3i & 1  \\    4 & 3i & -1  \\    20 & 3 & i  \\ \end{matrix} \right|\] Applying \[{{R}_{1}}\to {{R}_{1}}+{{R}_{2}}\]                                    \[=\left| \begin{matrix}    6i+4 & 0 & 0  \\    4 & 3i & -1  \\    20 & 3 & i  \\ \end{matrix} \right|\]                                    \[=(6i+4)\,(3{{i}^{2}}+3)\]                                    = 0 But \[\left| \begin{matrix}    6i & -3i & 1  \\    4 & 3i & -1  \\    20 & 3 & i  \\ \end{matrix} \right|=x+i\,y\] \[\Rightarrow \]   \[0+0i=x+i\,y\] \[\Rightarrow \]   \[x=0,\,\,y=0\]


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