CET Karnataka Engineering CET - Karnataka Engineering Solved Paper-2009

  • question_answer
    If \[f(x)=\int_{-1}^{x}{|t|\,\,dt,}\]  then for any \[x\ge 0,\] \[f(x)\]equal to

    A)  \[1-{{x}^{2}}\]

    B)  \[\frac{1}{2}(1+{{x}^{2}})\]

    C)  \[1+{{x}^{2}}\]

    D)  \[\frac{1}{2}(1-{{x}^{2}})\]           

    Correct Answer: B

    Solution :

    Given,  \[f(x)=\int_{-1}^{x}{|t|\,\,dt}\] \[=\int_{-1}^{0}{|t|\,\,dt}+\int_{0}^{x}{|t|\,dt}\] \[=\int_{-1}^{0}{-t\,\,dt\,+\int_{0}^{x}{t\,\,dt}}\] \[=-\left[ \frac{{{t}^{2}}}{2} \right]_{-1}^{0}+\left[ \frac{{{t}^{2}}}{2} \right]_{0}^{x}=-\left[ 0-\frac{1}{2} \right]+\left[ \frac{{{x}^{2}}}{2}-0 \right]\] \[=\frac{1}{2}(1+{{x}^{2}})\]


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