BCECE Engineering BCECE Engineering Solved Paper-2011

  • question_answer
    If \[f(x)=\int_{-1}^{x}{|t|dt,x\ge -1,}\]then

    A)  \[f\]and\[f\] are continuous for \[x+1>0\]

    B)         \[f\]is continuous but \[f\] is not continuous for \[x+1>0\]

    C)        \[f\] and\[f\] are not continuous at \[x=0\]

    D)         \[f\]is continuous at \[x=0\]but\[f\] is not so

    Correct Answer: A

    Solution :

    Given function can be denned as, \[f(x)=\left\{ \begin{matrix}    -1/2({{x}^{2}}-1),-1\le x<0  \\    1/2({{x}^{2}}+1),x\ge 0\,\,\,\,\,\,\,  \\ \end{matrix} \right.\] \[\Rightarrow \]    \[f(x)\left\{ \,\,\,\,\,\begin{matrix}    -x,-1<x<0\,\,\,\,\,\,\,  \\    0,x=0\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\    x,x>0\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,  \\ \end{matrix} \right.\] At\[x=0f({{0}^{-}})=\frac{1}{2},f({{0}^{+}})=\frac{1}{2},f(0)=\frac{1}{2}\] \[\therefore \] \[f\] is continuous at \[x=0.\]                 For \[f,f({{0}^{-}}),f(0),f({{0}^{+}})=0\]  \[\therefore \]\[f\] is also continuous at \[x=0.\] Thus, both \[f\] and\[f\] are continuous at \[x=0.\] Hence, both are continuous for \[x>-1.\]


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