RAJASTHAN ­ PET Rajasthan PET Solved Paper-2005

  • question_answer
    In the interval\[[-1,2],\]function\[f(x)=|x|+|x-1|\]will be

    A)  constant         

    B)  increasing

    C)  decreasing       

    D)  None of these

    Correct Answer: D

    Solution :

     Given,\[f(x)=|x|+|x-1|\]and interval\[[-1,2]\] \[f(x)=\left\{ \begin{matrix}    -2x+1 & , & -1\le x<0  \\    +1 & , & 0\le x<1  \\    2x-1 & , & 1\le x\le 2  \\ \end{matrix} \right.\] \[f'(x)=\left\{ \begin{matrix}    -2 & , & -1\le x<0  \\    does\text{ }not\text{ }exist & , & x=0  \\    0 & , & 0<x<1  \\    does\text{ }not\text{ }exist & , & x=1  \\    2 & , & 1<x\le 2  \\ \end{matrix} \right.\] Hence,\[f(x)\]is decreasing in the interval\[[-1,0[\]and increasing in\[\left] 1,2 \right]\]. ie,\[f(x)\]is neither decreasing nor increasing in the interval\[[-1,2]\].


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