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JEE Main & Advanced JEE Main Paper (Held On 11 April 2015)

  • question_answer
    \[\left| \begin{matrix}    {{x}^{2}}+x & x+1 & x-2  \\    2{{x}^{2}}+3x-1 & 3x & 3x-3  \\    {{x}^{2}}+2x+3 & 2x-1 & 2x-1  \\ \end{matrix} \right|=ax-12,\]then 'a' is equal to : [JEE Main Online Paper (Held On 11 April 2015)]  

    A)  12

    B)  24

    C)  -12

    D)  -24

    Correct Answer: B

    Solution :

      Put x = 1 both side\[\Rightarrow \]\[\left| \begin{matrix}    2 & 2 & -1  \\    4 & 3 & 0  \\    6 & 1 & 1  \\ \end{matrix} \right|=a-12\] \[\Rightarrow \]\[a=24\]


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