Manipal Engineering Manipal Engineering Solved Paper-2008

  • question_answer
    The range of the function\[f\left( x \right)={{x}^{2}}+\frac{1}{{{x}^{2}}+1}\]is

    A) \[[1,\,\,\infty )\]                              

    B) \[[2,\,\,\infty )\]

    C) \[\left[ \frac{3}{2},\,\,\infty  \right)\]                     

    D)         None of these

    Correct Answer: A

    Solution :

    Given,\[f(x)={{x}^{2}}+\frac{1}{{{x}^{2}}+1}\] \[\therefore \]  \[f(x)={{x}^{2}}+\left( \frac{1}{{{x}^{2}}+1}-1 \right)+1\]                 \[=({{x}^{2}}+1)-\left( \frac{{{x}^{2}}}{{{x}^{2}}+1} \right)\]                 \[=1+{{x}^{2}}\left( 1-\frac{1}{{{x}^{2}}+1} \right)\]                 \[\ge 1,\,\forall x\in R\] Hence, range of\[f(x)\]is\[[1,\,\,\infty )\].


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