JCECE Engineering JCECE Engineering Solved Paper-2008

  • question_answer
    Function\[f(x)=\left\{ \begin{matrix}    x-1, & x<2  \\    2x-3, & x\ge 2  \\ \end{matrix} \right.\]is a continuous function

    A)  for\[x=2\] only

    B)  for all real values of \[x\] such that\[x\ne 2\]

    C)  for all real values of\[x\]

    D)  for all integral values of \[x\] only

    Correct Answer: C

    Solution :

    Key Idea Every polynomial function is continuous. Given, function is                 \[f(x)=\left\{ \begin{matrix}    x-1, & x<2  \\    2x-3, & x\ge 2  \\ \end{matrix} \right.\] Since, it is a polynomial function, so it is continuous for every value of \[x\] except at\[x=2.\] At           \[x=2,\,\,LHL=\underset{x\to {{2}^{-}}}{\mathop{\lim }}\,x-1\]                    \[=\underset{h\to 0}{\mathop{\lim }}\,\,\,2-h-1=1\]         \[RHL=\underset{x\to {{2}^{+}}}{\mathop{\lim }}\,2x-3\]                    \[=\underset{h\to 0}{\mathop{\lim }}\,2(2+h)-3=1\] and \[f(2)=2(2)-3=1\] \[\therefore \]    \[LHL=RHL=f(2)\] Thus, \[f(x)\] is continuous for all real values of\[x\].


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