J & K CET Engineering J and K - CET Engineering Solved Paper-2008

  • question_answer
    If the  function  s\[f:R\to R\] given  by \[f(x)=\left\{ \begin{matrix}    x+a, & if & x\le 1  \\    3-{{x}^{2}}, & if & x>1  \\ \end{matrix} \right.\] is continuous at \[x=1,\] then a is equal to

    A)  \[4\]              

    B)  \[3\]

    C)  \[2\]              

    D)  \[1\]

    Correct Answer: D

    Solution :

    Given,   \[f(x)=\left\{ \begin{matrix}    x+a, & if & x\le 1  \\    3-{{x}^{2}}, & if & x>1  \\ \end{matrix} \right.\] LHL= \[\underset{x\to {{1}^{-}}}{\mathop{\lim }}\,\,\,f(x)\,=\underset{h\to 0}{\mathop{\lim }}\,\,\,1-h+a=1+a\] RHL= \[\underset{x\to {{1}^{+}}}{\mathop{\lim }}\,\,\,f(x)\,=\underset{h\to 0}{\mathop{\lim }}\,\,\,3-{{(1+h)}^{2}}=2\] Since,  \[f(x)\] is continuous at \[x=1.\] \[\therefore \] \[LHL=RHL\] \[\Rightarrow \]  \[1+a=2\,\,\,\Rightarrow \,\,a=1\]


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