JEE Main & Advanced AIEEE Solved Paper-2013

  • question_answer
    The number of values of k, for which the system of equations: \[(k+1)x+8y=4k\] \[kx+(k+3)y=3k-1\] has no solution, is:     AIEEE Solevd Paper-2013

    A) in finite                                

    B) 1                             

    C)        2                             

    D)        3

    Correct Answer: B

    Solution :

    \[\Delta =\left| \begin{matrix}    k+1 & 8  \\    k & k+3  \\ \end{matrix} \right|={{k}^{2}}+4k+3-8k\] \[={{k}^{2}}-4k+3\] \[=(k-3)(k-1)\] \[{{\Delta }_{1}}=\left| \begin{matrix}    4k & 8  \\    3k-1 & k+3  \\ \end{matrix} \right|=4{{k}^{2}}+12k-24k+8\] \[=4{{k}^{2}}-12k+8\] \[=4({{k}^{2}}-3k+2)\] \[=4(k-2)(k-1)\] \[{{\Delta }_{2}}=\left| \begin{matrix}    k+1 & 4k  \\    k & 3k-1  \\ \end{matrix} \right|=3{{k}^{2}}+2k-1-4{{k}^{2}}\] \[=-{{k}^{2}}+2k-1\] \[=-{{(k-1)}^{2}}\] As given no solution\[\Rightarrow {{\Delta }_{1}}\And {{\Delta }_{2}}\ne 0\] But \[\Delta =0\] \[\Rightarrow \]\[k=3\]


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