CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2009

  • question_answer
    If  \[\left| \begin{matrix}    x+1 & x+2 & x+a  \\    x+2 & x+3 & x+b  \\    x+3 & x+4 & x+c  \\ \end{matrix} \right|=0,\] then a, b, c are

    A)  in GP                                   

    B)  in HP

    C)  equal                                   

    D)  in AP

    Correct Answer: D

    Solution :

    Given,    \[\left| \begin{matrix}    x+1 & x+2 & x+a  \\    x+2 & x+3 & x+b  \\    x+3 & x+4 & x+c  \\ \end{matrix} \right|=0\] Applying \[{{R}_{1}}\to {{R}_{1}}+{{R}_{3}}-2{{R}_{2}},\] we get                 \[\left| \begin{matrix}    0 & 0 & a+c-2b  \\    x+2 & x+3 & x+b  \\    x+3 & x+4 & x+c  \\ \end{matrix} \right|=0\] \[\Rightarrow \]               \[(a+c-2b)(-1)=0\] \[\Rightarrow \]               \[2b=a+c\] \[\Rightarrow \]               \[a,b,c\] are AP.


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