CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    The value of\[x\]in the interval [4, 9] at which the function\[f(x)=\sqrt{x}\] satisfies the mean value theorem is

    A)  \[\frac{13}{4}\]                               

    B)  \[\frac{17}{4}\]

    C)  \[\frac{21}{4}\]               

    D)         \[\frac{23}{4}\]

    E)  \[\frac{25}{4}\]

    Correct Answer: E

    Solution :

    Function\[f(x)=\sqrt{x}\]and\[[4,\text{ }9]\] Here,\[a=4\]and\[b=9\] \[f(a)=f(4)=2\]and \[f(b)=f(9)=3\] By Lagranges mean value theorem, \[\Rightarrow \]               \[\frac{f(b)-f(a)}{b-a}=f(x)\] \[\Rightarrow \]               \[\frac{3-2}{9-4}=\frac{1}{2\sqrt{x}}\] \[\Rightarrow \]               \[\frac{1}{2\sqrt{x}}=\frac{1}{5}\] \[\Rightarrow \]               \[x=\frac{25}{4}\] Which lies in the given interval\[[4,\text{ }9]\].


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