J & K CET Engineering J and K - CET Engineering Solved Paper-2003

  • question_answer
    If \[f(x)={{x}^{2}}+4x+1,\] then

    A)  \[f(x)=f(-x),\] for all x

    B)  \[f(x)\ne 1,\] for \[x=0\]

    C)  \[f''(x)>0,\] for all x

    D)  \[f(x)>1,\] for \[x\le 1\]

    Correct Answer: C

    Solution :

    Given that, \[f(x)={{x}^{2}}+4x+1\] \[f'(x)=2x+4\] For maxima or minima, put \[f'(x)=0\] \[\Rightarrow \] \[2x+4=0\] \[\Rightarrow \] \[x=-2\] Now, \[f''(x)=2>0\]


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